GIT HELP for Mac Os/Unix. (windows will be on the way). I had downloaded the Git Tower client app for Mac to start with (I was not very familiar with the command line yet and thought this would be the safer option). So I cloned the repository and worked on the files for a whole day.
I second Tower. It's the best Git client for OSX by far! I use it for multiple clients and multiple hosting providers.
One thing to note is that it is advertised as SVN friendly, but I find that to be false. I don't use it for SVN, so it works out fine, but just do not purchase it with the intent of using SVN with it too. And I find the support via Twitter (@gittower) to be better than filling out a report on their website. The second best is emailing them directly ([email protected]). If all else fails, fill out the form and say a prayer! It is a bit of money, but it is WELL worth it in my opinion. It is not yet available on Windows, but SmartGIT is the best (and only, to a certain extent) GUI that is available on OSX and Windows (and Linux, if thats your thing).
And its free for personal, non-commercial use too. Best of luck!