I've been using the Git command line tools to setup my workspaces against GitHub and then importing projects into Eclipse going back and forth to the command line to diff, commit and push back to origin. In my current project I've discovered the Git Repository Explorer in Eclipse and how it makes many of the tasks much easier.
To clone an existing GitHub repository add the perspective Git Repository Explorer
Choose to clone a repository
Select the branch to check out and in the next view tick the "Import all existing projects after clone finishes"
Now the usual Eclipse goodies har here for you, to diff local changes is much clearer than the command line diff utility for example
The synchronize option to see all changes in your local copy
Inspecting the history of the file is also presented in a more readable manner
Commit and push to origin (GitHub in this case) is a single operation if you wish