We just changed our Subversion repository's url from something terrible with custom port number hideousness to a URL so clean, concise and georgeous that I became brain damaged. The old URL still works but I wanted to repoint all my checked out code to the new URL. I tried switch and it didn't work until Bret mentioned that Eclipse had something called relocate for this issue. A google search later...
svn switch --relocate <from URL> <to URL>
I should have known all of this and likely did at one point but it just fell out of my brain.