There is a link to this on the page, but I can't tell you how valuable HTTP Client (also by Todd Ditchendorf) is for testing miscellaneous APIs quickly. http://ditchnet.org/httpclient/ The ability to save requests and load them up later is a nice touch.
Something that could have saved me a load of time earlier. I spent a solid three days trying to get yacc to play well with ObjC. I'll check this out this weekend.