Hello, although this isn't directly involving bullet implementation by myself, I did some scripts in Blender which use Bullet heavily for the simulation part.
Heaper is a very simple script for making big natural looking heaps.
Crackme are currently actually 2 scripts, where 1 is for generating broken glass tables/walls/grounds, and the other one can split any manifold mesh into shards.
More info is in this thread:http://blenderartists.org/forum/showthread.php?p=1292960#post1292960
downloadable files and video examples/images are here:http://plant.ffa.vutbr.cz/~novak/dwnflz/crackme/
There are some things which I hit during making the tests/setups with these tools. They are rather blender-side implementation issues, so dunno if I should ask here. Number 1 issue is nice releasing of shards based on impact point and power of impact. The getReactionForce() function isn't callable for objects which haven't physic simulation on(not-released shards) which is crucial for the releasing of shards with proper power. Also, it could be used to setup/brake constraints and simulating different effects like that.
Another one is creating of meshes directly in engine during the playback of simulation(because of use of point of impact), or rather running the simulation without the game engine and doing the splitting process during it. There is currently no access to starting the simulation from a script and possibly reading force/hit values during the simulation, so there would be the possibility to interrupt the simulation, replace the meshes with sharded meshes, then continue the simulation?
Other thing is that there's still no acces to logicbricks in the engine, and I use the logicbricks for chain reactions currently. That's an issue which is supposed to be solved with 2.5.
I'd want in the future implement these tools deeper into blender, so they could better cooperate with blender's animation system, but so-far I was satisfied with the results from the python code, which is quickly tweakable.
Thanks for the great bullet library, I was again surprised by it's stability and performance for such uses.