I tried WebKut when it was first launched and then revisited it this morning.
A screen capture utility, WebKut's latest version now easily moves it into the top-5 in that category (a freeware category that's been around for a LONG time).
Note: The Fireshot add-on for Firefox is still our no. 1
Lightweight, virtually no learning curve, auto-upload to Flickr and more, the cross-platform app built on the Adobe Air 1.1 platform just works.
WebKut is donationware. You can download a copy here.