At $work we use CVS (but may shift to SVN). At home for developing small Perl based projects I use Subversion. In both places I use Windows and either TortoiseCVS or TortoiseSVN. Tortoise takes a lot of the pain out of using either product.

For home use SVN is easy to set up and maintain and with Tortoise integrates very nicely with Explorer (under Windows). I also have a small SVN server hosted for me by a friend that I use to manage the PMEdit project. Again that was easy to set up and is easy to use. One of my reasons for using a RCS at home is because I work on a couple of machines (laptop and desktop).

I had a brief look at Monotone, but without a client I didn't persist with it. How it pans out with regular use I don't know, but it is somewhat different to the RCS's I'm familiar with.

Update: I should add that there are some important differences between CVS and SVN. Most important is that CVS deals with files - it has no idea of the relationships between files nor any way of tracking files if they move, are refactored or change their names. SVN on the other hand deals with the whole repository - a commit is an update of the state of the whole repository and thus tracks directory structure and file name and location related changes.

Branching and tagging are quite different between CVS and SVN too. One result of this is that some tagging operations that can be expensive for CVS cost almost nothing for SVN - not a big issue for home use, but something that hits us hard at work every day!