Bullet 2.80 includes a preview of the GPU rigid body pipeline by Takahiro Harada, running 100% on the GPU using OpenCL. You can check out the Youtube videos or slides and precompiled binaries.
A new AMD Radeon 7970 Tahiti can simulate 110k objects in real-time between 15-30 frames/second. It also works on recent NVIDIA GPUs with latest drivers.

Graham Rhodes and Anthony Hamilton contributed a Android/NEON optimized version of Sony Physics Effects, which will be used as a handheld backend in Bullet 3.x. Last but not least, the open source Dynamica Bullet plugin for Maya is now deterministic and has preliminary support for soft body/cloth and convex decomposition through HACD.

For more info, see this forum post.