http://forum.maratis3d.com/viewtopic.php?id=522 Rayhit function
http://forum.maratis3d.com/viewtopic.php?id=509 Bullet script
http://forum.maratis3d.com/viewtopic.php?id=508 Adding gravity

http://forum.maratis3d.com/viewtopic.php?id=514 Making text not colliding with objects
http://forum.maratis3d.com/viewtopic.php?id=506 If models too dark
http://forum.maratis3d.com/viewtopic.php?id=505 Characters and how animation affect physics.

Oh yeah, and dont forget this tutorial: http://www.dev-hq.net/lua/

It's great.