Found via Weblog Tools Collection, here is a page that looks very promising and interesting : htaccess generator.
Not only it seems to be handy when it comes to create (simple, I guess, but still) rules, but I noticed while scrolling down the page a lot of other interesting links (PHP regexp tester for example)
Now, the problem is : what sort of silly mod_rewrite rule can I pretend to need so I can test the thing ?