Make user-defined size screenshots of websites.
Paparazzi! is a small utility for Mac OS X that makes screenshots of webpages. This very simple tool takes screenshots of websites which do not fit on one screen. You specify the desired width, minimal height and the URL. The program displays a preview and you can save the screenshot to PNG, JPEG, TIFF, or PDF.
It's written in Objective-C using the Cocoa API and the WebKit framework... It was inspired by webkit2png which is a commandline tool written by Paul Hammond in pyObjC, so all intellectual credit for the basic functionality goes to him ;)