Simple 301 Redirects provides an easy method of redirecting requests to another page on your site or elsewhere on the web.
Figures after I proclaim the greatness of the plugin it inconsistently fails for me. Not sure exactly why because my process has been the same for each site, but who knows what is causing the conflict. Either way, I'd prefer not to rate this plugin at all, but since I can't delete my rating I'm lowering it to 3 stars for the inconsistency. Having looked through the support forums, I'm not the only one that has had the same problem. So, use at your own discretion and test, test, test!
I had to a multi-site blog to another domain with a different URL and blog structure. Had to redirect a lot of old URLs. Would've been a nightmare given how not user friendly doing it yourself with mod_rewrite is on Apache. (see http://httpd.apache.org/docs/2.0/misc/rewriteguide.html). This plugin makes it a snap, puts everything I need to keep track of in an easy to find spot in the admin, and uses 301 permanent redirects. Does everything I ask!