We keep most of our projects in Subversion repositories. If you're not familiar with Subversion, here are some tutorials, tips and resources to get you started.
Here are some graphical Subversion clients.
Here is a short TortoiseSVN tutorial.
And here is a short class on RapidSVN.
But please folks, USE THE COMMAND LINE! It only hurts a little in the beginning; after that it's all gravy.
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