I heard about SCPlugin for OS X at cf.objective() 2008. It's a Finder plugin for OS X that lets you manipulate SVN repos, much like TortoiseSVN for Windows.

Once installed, SCPlugin knows when a directory in OS X is under source control from SVN, and shows you icons on the contained files (again, just like TortoiseSVN). You can then perform SVN operations by right clicking files and navigating to the More => Subversion submenu.

I've only used it a little so far, but it seems stable and easy to use.