I found a nice Firefox plugin called Poster that allows you to act as a REST client similar to rest-client and the others. I wish it would render the response to a firefox tab (rather than a custom output window) so any returned XML could be colorized by Firefox's awesome syntax highlighting. But overall seems to work OK.
Update: Oh, even better. I found another firefox plugin callsed RestClient https://addons.mozilla.org/en-US/firefox/addon/9780. This seems to do the syntax highlighting.
