I use SQLite Database Browser for SQLite3 currently and it's pretty useful. Works across Windows/OS X/Linux and is lightweight and fast. Slightly unstable with executing SQL on the DB if it's incorrectly formatted.
Edit: I have recently discovered SQLite Manager, a plugin for Firefox. Obviously you need to run Firefox, but you can close all windows and just run it "standalone". It's very feature complete, amazingly stable and it remembers your databases! It has tonnes of features so I've moved away from SQLite Database Browser as the instability and lack of features is too much to bear.
