BuddyPress.org

First, you have to change all references to the strings you want to localize so your POT file knows where to reference them.
Then, you need to create a POT file.

Here’s a quick guide I found on Google using poEdit:
http://weblogtoolscollection.com/archives/2007/08/27/localizing-a-wordpress-plugin-using-poedit/

There are others of course!

If you have any Qs, reply back.