Unfuddle's forums has a discussion on alternate Subversion clients for Mac users.

SCPlugin is a free Subversion plugin that integrates with the Finder, and works similar to TortoiseSVN (a Windows SVN explorer plugin). Syncro SVN is a commercial standalone SVN client ($60) that works on Mac, Windows, and Linux.

Most Mac users use the svn command line program, but I know from experience how handy TortoiseSVN is for me to visually view the state of my working folder, compare files, and other operations.