I've used the following
GitHub for Windows - required me to download installer which took a long time for me to install. UI was too basic for me and at that time was very slow even when using a local repository.
SourceTree - UI looks goods but under delivers on features when compared to GitEye and SmartGit.
Collabnet GitEye (site) - UI is famililar to Eclipse users just like me. Worked great and especially had a credential store (SecureStore) which inspired some confidence in how it handles storing of passwords plus SSH key management.
SmartGit (site) - offers personal and commercial versions but even the personal version is an absolute pleasure to use. Staging files, looking at logs, reverting, committing, pushing etc. The features were sufficient for me.
I'd recommend the last two especially SmartGit since the UI is user friendly and pushing to more than 1 repository is much easier.
My answer is not really that verbose but please try to download and see for yourself.