TortoiseSVN is an easy to use SCM / source control software for Microsoft Windows and maybe the best standalone Subversion client there is. It is implemented as a Windows shell extension, which makes it integrate seamlessly into the Windows explorer. Since its not an integration for a specific IDE you can use it with whatever development tools you like.
Another advantage of this shell integration is that not only web or software developers can use it but all the people who dont have the development tools installed, for example translators, doc writers etc.
TortoiseSVN allows you to use TortoiseMerge easily, without changing your custom different tool setup: just hold down the shift-key when you click on the context menu to do the diff. If the shift key is pressed when doing a diff, TortoiseSVN always uses TortoiseMerge. If the shift key is not pressed, the diff/merge tool specified in your settings is used.
Moving and renaming versioned files inside a working copy must always be done with the corresponding Subversion/TortoiseSVN commands. A move/rename without those (e.g., with the Windows Explorer) leads to problems since Subversion doesnt know that you have moved/renamed the files.