I use subversion (have for years via the command line) but in this new job I am keeping files on my Mac and not the server. I installed the command line tool and SCPlugin for fun but it turns out to be so handy I use it primarily now.

Right click (or control click) on an icon (single file or a folder) and towards the bottom there'll be all your subversion commands. In Leopard they are under the 'More' menu in Panther they are in the first menu (this might be set is some finder preferences that I haven't come across yet).

SCPlugin puts a green (svn up to date), yellow (svn knows nothing) or red (modified) mark on the files icon which makes it really easy to see what's changed.

It works with BBEdit's svn functions, then command line tools and, I presume, others or just by itself.