For the Mac, there’s SCPlugin, which seems to offer similar functionality and Finder integration. Of course, there are a couple additional (and, in my opinion, poorly-documented) steps required to use SCPlugin with an svn+ssh connection. (Note: these steps worked for me on OS X 10.5, Leopard. YMMV)

1. Get SCPlugin from http://scplugin.tigris.org/ and install it. There is no need for a separate installation for SVN – SVN 1.4.4 appears to come pre-installed on Leopard.
2. Restart the Finder. I just opened up Force Quit (Command-Option-Escape) and chose to Relaunch Finder.app, but you can also just log out and log back in if Force Quit scares you.
3. Here’s the tricky part – you need to set up ssh to use key pair authentication as opposed to password authentication when you connect to your SSH server. Detailed instructions can be found here.
4. Now check something out using SCPlugin. In Leopard, this is done by right-clicking in the target directory in a Finder window, choosing “More,” “Subversion,” “Checkout,” and entering the repository URL and other information as necessary.