Is there some online forwarding service that I can give HTTP GET parameters to, and it would create a form with the parameters and submit it as POST?
For example, I'd like to give someone the URL:
http://imaginaryservice.com/http://reddit.com/post/login?username=guy&password=fawkes
...and when they click it, it should do the equivalent of submitting those parameters in POST to that URL (though the referer header would obviously reveal the trick).
Anyway, I know how I'd build one, but if something like that already exists, I'd like to know.