FireFox has an add-on ext for Image shack..... Just right click the picture in question to save to I-shack and up pops your pic w/url ...
Hmm. Looks like it worked (Rehost Image)! That was really easy!
I see there are also some extensions that address the problem for Photobucket.
I also use a Greasemonkey script that saves typing while on the posting form. In this case, I just clicked the Image button, pasted the URL, and the script threw an IMG tag around it. You can get the script by clicking my name below.