Bullet is available using apt-get on Ubuntu. You can find more general instructions at the bullet installation page.
sudo apt-get install libbullet-dev libbullet-doc libbullet-extras-dev
git clone https://bitbucket.org/alexeyknyshev/ogrebullet.git cd ogrebullet mkdir build cd build cmake .. make sudo make install
The make command failed so I had to fix the file ogrebullet/Collisions/include/Utils/OgreBulletCollisionMeshToShapeConverter.h on line 100 the line:
StaticMeshToShapeConverter(Ogre::Entity *entityshould read:
StaticMeshToShapeConverter(const Ogre::Entity *entityIt builds, I really hope I didn't break anything!