Awhile I posted about ScreenGrab, an extension for Firefox that takes a screenshot of an entire web page. It got the job done, but I had a few issues with it, namely that it required Java and it was a tad buggy. Pearl Crescent's Page Saver looks like a great alternative. It's only for Firefox 1.5 and above and uses the Canvas feature to capture either the visible portion of the page or the whole thing without your having to do so much touch your scrollbar. The only caveat is that at this point it isn't able to capture the output of plugins such as Flash.