Here is a list of all files with brief descriptions:

Extras
Serialize
BulletFileLoader
autogenerated
bullet.h
bChunk.cpp
bChunk.h
bCommon.h
bDefines.h
bDNA.cpp
bDNA.h
bFile.cpp
bFile.h
btBulletFile.cpp
btBulletFile.h
BulletWorldImporter
btBulletWorldImporter.cpp
btBulletWorldImporter.h
btWorldImporter.cpp
btWorldImporter.h
src
BulletCollision
BroadphaseCollision
btAxisSweep3.cpp
btAxisSweep3.h
btAxisSweep3Internal.h
btBroadphaseInterface.h
btBroadphaseProxy.cpp
btBroadphaseProxy.h
btCollisionAlgorithm.cpp
btCollisionAlgorithm.h
btDbvt.cpp
btDbvt.h
btDbvtBroadphase.cpp
btDbvtBroadphase.h
btDispatcher.cpp
btDispatcher.h
btOverlappingPairCache.cpp
btOverlappingPairCache.h
btOverlappingPairCallback.h
btQuantizedBvh.cpp
btQuantizedBvh.h
btSimpleBroadphase.cpp
btSimpleBroadphase.h
CollisionDispatch
btActivatingCollisionAlgorithm.cpp
btActivatingCollisionAlgorithm.h
btBox2dBox2dCollisionAlgorithm.cpp
btBox2dBox2dCollisionAlgorithm.h
btBoxBoxCollisionAlgorithm.cpp
btBoxBoxCollisionAlgorithm.h
btBoxBoxDetector.cpp
btBoxBoxDetector.h
btCollisionConfiguration.h
btCollisionCreateFunc.h
btCollisionDispatcher.cpp
btCollisionDispatcher.h
btCollisionDispatcherMt.cpp
btCollisionDispatcherMt.h
btCollisionObject.cpp
btCollisionObject.h
btCollisionObjectWrapper.h
btCollisionWorld.cpp
btCollisionWorld.h
btCollisionWorldImporter.cpp
btCollisionWorldImporter.h
btCompoundCollisionAlgorithm.cpp
btCompoundCollisionAlgorithm.h
btCompoundCompoundCollisionAlgorithm.cpp
btCompoundCompoundCollisionAlgorithm.h
btConvex2dConvex2dAlgorithm.cpp
btConvex2dConvex2dAlgorithm.h
btConvexConcaveCollisionAlgorithm.cpp
btConvexConcaveCollisionAlgorithm.h
btConvexConvexAlgorithm.cpp
btConvexConvexAlgorithm.h
btConvexPlaneCollisionAlgorithm.cpp
btConvexPlaneCollisionAlgorithm.h
btDefaultCollisionConfiguration.cpp
btDefaultCollisionConfiguration.h
btEmptyCollisionAlgorithm.cpp
btEmptyCollisionAlgorithm.h
btGhostObject.cpp
btGhostObject.h
btHashedSimplePairCache.cpp
btHashedSimplePairCache.h
btInternalEdgeUtility.cpp
btInternalEdgeUtility.h
btManifoldResult.cpp
btManifoldResult.h
btSimulationIslandManager.cpp
btSimulationIslandManager.h
btSphereBoxCollisionAlgorithm.cpp
btSphereBoxCollisionAlgorithm.h
btSphereSphereCollisionAlgorithm.cpp
btSphereSphereCollisionAlgorithm.h
btSphereTriangleCollisionAlgorithm.cpp
btSphereTriangleCollisionAlgorithm.h
btUnionFind.cpp
btUnionFind.h
SphereTriangleDetector.cpp
SphereTriangleDetector.h
CollisionShapes
btBox2dShape.cpp
btBox2dShape.h
btBoxShape.cpp
btBoxShape.h
btBvhTriangleMeshShape.cpp
btBvhTriangleMeshShape.h
btCapsuleShape.cpp
btCapsuleShape.h
btCollisionMargin.h
btCollisionShape.cpp
btCollisionShape.h
btCompoundShape.cpp
btCompoundShape.h
btConcaveShape.cpp
btConcaveShape.h
btConeShape.cpp
btConeShape.h
btConvex2dShape.cpp
btConvex2dShape.h
btConvexHullShape.cpp
btConvexHullShape.h
btConvexInternalShape.cpp
btConvexInternalShape.h
btConvexPointCloudShape.cpp
btConvexPointCloudShape.h
btConvexPolyhedron.cpp
btConvexPolyhedron.h
btConvexShape.cpp
btConvexShape.h
btConvexTriangleMeshShape.cpp
btConvexTriangleMeshShape.h
btCylinderShape.cpp
btCylinderShape.h
btEmptyShape.cpp
btEmptyShape.h
btHeightfieldTerrainShape.cpp
btHeightfieldTerrainShape.h
btMaterial.h
btMinkowskiSumShape.cpp
btMinkowskiSumShape.h
btMultimaterialTriangleMeshShape.cpp
btMultimaterialTriangleMeshShape.h
btMultiSphereShape.cpp
btMultiSphereShape.h
btOptimizedBvh.cpp
btOptimizedBvh.h
btPolyhedralConvexShape.cpp
btPolyhedralConvexShape.h
btScaledBvhTriangleMeshShape.cpp
btScaledBvhTriangleMeshShape.h
btShapeHull.cpp
btShapeHull.h
btSphereShape.cpp
btSphereShape.h
btStaticPlaneShape.cpp
btStaticPlaneShape.h
btStridingMeshInterface.cpp
btStridingMeshInterface.h
btTetrahedronShape.cpp
btTetrahedronShape.h
btTriangleBuffer.cpp
btTriangleBuffer.h
btTriangleCallback.cpp
btTriangleCallback.h
btTriangleIndexVertexArray.cpp
btTriangleIndexVertexArray.h
btTriangleIndexVertexMaterialArray.cpp
btTriangleIndexVertexMaterialArray.h
btTriangleInfoMap.h
btTriangleMesh.cpp
btTriangleMesh.h
btTriangleMeshShape.cpp
btTriangleMeshShape.h
btTriangleShape.h
btUniformScalingShape.cpp
btUniformScalingShape.h
Gimpact
btBoxCollision.h
btClipPolygon.h
btCompoundFromGimpact.h
btContactProcessing.cpp
btContactProcessing.h
btContactProcessingStructs.h
btGenericPoolAllocator.cpp
btGenericPoolAllocator.h
btGeometryOperations.h
btGImpactBvh.cpp
btGImpactBvh.h
btGImpactBvhStructs.h
btGImpactCollisionAlgorithm.cpp
btGImpactCollisionAlgorithm.h
btGImpactMassUtil.h
btGImpactQuantizedBvh.cpp
btGImpactQuantizedBvh.h
btGImpactQuantizedBvhStructs.h
btGImpactShape.cpp
btGImpactShape.h
btQuantization.h
btTriangleShapeEx.cpp
btTriangleShapeEx.h
gim_array.h
gim_basic_geometry_operations.h
gim_bitset.h
gim_box_collision.h
gim_box_set.cpp
gim_box_set.h
gim_clip_polygon.h
gim_contact.cpp
gim_contact.h
gim_geom_types.h
gim_geometry.h
gim_hash_table.h
gim_linear_math.h
gim_math.h
gim_memory.cpp
gim_memory.h
gim_radixsort.h
gim_tri_collision.cpp
gim_tri_collision.h
NarrowPhaseCollision
btComputeGjkEpaPenetration.h
btContinuousConvexCollision.cpp
btContinuousConvexCollision.h
btConvexCast.cpp
btConvexCast.h
btConvexPenetrationDepthSolver.h
btDiscreteCollisionDetectorInterface.h
btGjkCollisionDescription.h
btGjkConvexCast.cpp
btGjkConvexCast.h
btGjkEpa2.cpp
btGjkEpa2.h
btGjkEpa3.h
btGjkEpaPenetrationDepthSolver.cpp
btGjkEpaPenetrationDepthSolver.h
btGjkPairDetector.cpp
btGjkPairDetector.h
btManifoldPoint.h
btMinkowskiPenetrationDepthSolver.cpp
btMinkowskiPenetrationDepthSolver.h
btMprPenetration.h
btPersistentManifold.cpp
btPersistentManifold.h
btPointCollector.h
btPolyhedralContactClipping.cpp
btPolyhedralContactClipping.h
btRaycastCallback.cpp
btRaycastCallback.h
btSimplexSolverInterface.h
btSubSimplexConvexCast.cpp
btSubSimplexConvexCast.h
btVoronoiSimplexSolver.cpp
btVoronoiSimplexSolver.h
BulletDynamics
Character
btCharacterControllerInterface.h
btKinematicCharacterController.cpp
btKinematicCharacterController.h
ConstraintSolver
btConeTwistConstraint.cpp
btConeTwistConstraint.h
btConstraintSolver.h
btContactConstraint.cpp
btContactConstraint.h
btContactSolverInfo.h
btFixedConstraint.cpp
btFixedConstraint.h
btGearConstraint.cpp
btGearConstraint.h
btGeneric6DofConstraint.cpp
btGeneric6DofConstraint.h
btGeneric6DofSpring2Constraint.cpp
btGeneric6DofSpring2Constraint.h
btGeneric6DofSpringConstraint.cpp
btGeneric6DofSpringConstraint.h
btHinge2Constraint.cpp
btHinge2Constraint.h
btHingeConstraint.cpp
btHingeConstraint.h
btJacobianEntry.h
btNNCGConstraintSolver.cpp
btNNCGConstraintSolver.h
btPoint2PointConstraint.cpp
btPoint2PointConstraint.h
btSequentialImpulseConstraintSolver.cpp
btSequentialImpulseConstraintSolver.h
btSliderConstraint.cpp
btSliderConstraint.h
btSolve2LinearConstraint.cpp
btSolve2LinearConstraint.h
btSolverBody.h
btSolverConstraint.h
btTypedConstraint.cpp
btTypedConstraint.h
btUniversalConstraint.cpp
btUniversalConstraint.h
Dynamics
btActionInterface.h
btDiscreteDynamicsWorld.cpp
btDiscreteDynamicsWorld.h
btDiscreteDynamicsWorldMt.cpp
btDiscreteDynamicsWorldMt.h
btDynamicsWorld.h
btRigidBody.cpp
btRigidBody.h
btSimpleDynamicsWorld.cpp
btSimpleDynamicsWorld.h
btSimulationIslandManagerMt.cpp
btSimulationIslandManagerMt.h
Featherstone
btMultiBody.cpp
btMultiBody.h
btMultiBodyConstraint.cpp
btMultiBodyConstraint.h
btMultiBodyConstraintSolver.cpp
btMultiBodyConstraintSolver.h
btMultiBodyDynamicsWorld.cpp
btMultiBodyDynamicsWorld.h
btMultiBodyFixedConstraint.cpp
btMultiBodyFixedConstraint.h
btMultiBodyGearConstraint.cpp
btMultiBodyGearConstraint.h
btMultiBodyJointFeedback.h
btMultiBodyJointLimitConstraint.cpp
btMultiBodyJointLimitConstraint.h
btMultiBodyJointMotor.cpp
btMultiBodyJointMotor.h
btMultiBodyLink.h
btMultiBodyLinkCollider.h
btMultiBodyPoint2Point.cpp
btMultiBodyPoint2Point.h
btMultiBodySliderConstraint.cpp
btMultiBodySliderConstraint.h
btMultiBodySolverConstraint.h
MLCPSolvers
btDantzigLCP.cpp
btDantzigLCP.h
btDantzigSolver.h
btLemkeAlgorithm.cpp
btLemkeAlgorithm.h
btLemkeSolver.h
btMLCPSolver.cpp
btMLCPSolver.h
btMLCPSolverInterface.h
btPATHSolver.h
btSolveProjectedGaussSeidel.h
Vehicle
btRaycastVehicle.cpp
btRaycastVehicle.h
btVehicleRaycaster.h
btWheelInfo.cpp
btWheelInfo.h
BulletSoftBody
btDefaultSoftBodySolver.cpp
btDefaultSoftBodySolver.h
btSoftBody.cpp
btSoftBody.h
btSoftBodyConcaveCollisionAlgorithm.cpp
btSoftBodyConcaveCollisionAlgorithm.h
btSoftBodyData.h
btSoftBodyHelpers.cpp
btSoftBodyHelpers.h
btSoftBodyInternals.h
btSoftBodyRigidBodyCollisionConfiguration.cpp
btSoftBodyRigidBodyCollisionConfiguration.h
btSoftBodySolvers.h
btSoftBodySolverVertexBuffer.h
btSoftMultiBodyDynamicsWorld.cpp
btSoftMultiBodyDynamicsWorld.h
btSoftRigidCollisionAlgorithm.cpp
btSoftRigidCollisionAlgorithm.h
btSoftRigidDynamicsWorld.cpp
btSoftRigidDynamicsWorld.h
btSoftSoftCollisionAlgorithm.cpp
btSoftSoftCollisionAlgorithm.h
btSparseSDF.h
LinearMath
btAabbUtil2.h
btAlignedAllocator.cpp
btAlignedAllocator.h
btAlignedObjectArray.h
btConvexHull.cpp
btConvexHull.h
btConvexHullComputer.cpp
btConvexHullComputer.h
btCpuFeatureUtility.h
btDefaultMotionState.h
btGeometryUtil.cpp
btGeometryUtil.h
btGrahamScan2dConvexHull.h
btHashMap.h
btIDebugDraw.h
btList.h
btMatrix3x3.h
btMatrixX.h
btMinMax.h
btMotionState.h
btPolarDecomposition.cpp
btPolarDecomposition.h
btPoolAllocator.h
btQuadWord.h
btQuaternion.h
btQuickprof.cpp
btQuickprof.h
btRandom.h
btScalar.h
btSerializer.cpp
btSerializer.h
btSerializer64.cpp
btSpatialAlgebra.h
btStackAlloc.h
btThreads.cpp
btThreads.h
btTransform.h
btTransformUtil.h
btVector3.cpp
btVector3.h
btBulletCollisionCommon.h
btBulletDynamicsCommon.h