A Python command line utility I put together so I can use a master
password and have it generate a site specific password for each site
that needs a password. I'm in the process of adding a Javascript
implementation for use in a web browser and and an Android applet
implementation.

The passwords generated are carefully massaged to try to fit just
about every site's password requirements and keep at least 60 bits of
entropy in every password.

It uses the PKCS#5 v2.0 PBKDF2 with a large (but configurable) number
of iterations to make sure that even if an attacker manages to get the
plaintext password for a given site, it will be practically impossible
for them to reverse the hash and figure out the master password.

It has a small bug in which it skips 'Z', 'z' and '9' for generating the
uppercase, lowercase and digit characters. This bug should be faithfully
replicated to all the various implementations.