Rainbow tables 101

Read:
http://www.codinghorror.com/blog/2007/09/rainbow-hash-cracking.html
and
http://chargen.matasano.com/chargen/2007/9/7/enough-with-the-rainbow-tables-what-you-need-to-know-about-s.html

Use bcrypt:
http://code.google.com/p/py-bcrypt/