i have tried VisualSVN server for the PC, and it seems pretty easy to install and use. The only catch is that my PC with Vista does crash, or can become not so responsive sometimes, so I am thinking of using an SVN server on the Mac instead.
is there one on the Mac that is easy to install and is reliable too?
You could have a look at a program called "Versions" made by a company called "Sofa". versionsapp.com It's not free but it's really nice.
macsvnserver claims to be a drop-installable Subversion server for Mac OS X. Alternatively, you could use a remote Subversion hosting service like Beanstalk or Unfuddle to host your repository.
If you're using OS X 10.5 Server, you really should consider using the macports SVN. Macports is a single install and the SVN port automatically integrates with the system apache 2.0 including authenticating to OpenDirectory.