Subversion Client for Windows Vista

tortoiseSVN is very good.

There is always the trusty command line version of svn. I use this in addition to GUI versions, I have run into too many instances where the GUI version has a problem and I have to resort to the command line to fix it.

I have also used SmartSVN and been very happy with it. It is more of a full fledged client, rather than an extension to the explorer. This has some benefits, in that it will monitor and show you all your current changes and those pending changes.

SubClipse is great if you are using Eclipse.

I really like VisualSVN if you're using Visual Studio. It's free for a 30 day trial, then $49. Well worth the 50 bucks, in my opinion.

If you have to have free, and using Visual Studio, try AnkhSVN. I've used it before, and it works fine.