I've heard some about TortoiseSVN, I downloaded it, but I haven't got a chance to see what it's about. You can read a lot about it, and I'm sure you can find many more
through google. I've just googled a bit and came up with:
Note to be careful though, a lot of shell replacement programs also integrate their own programs into it, or spyware, etc.. However, something as simple as TortoiseSVN doesn't add any extra, just a few functions.