This one will take a jpg image of The ENTIRE SCREEN of the ENTIRE PAGE – you can set the width or change the width by altering the URL parameter at the end of the string (.jpg&w=640)

http://www.thumbalizr.com/app/thumbs/php/?src=/app/thumbs/23e8a2962df7373d8424b82a72ff23d7.jpg&w=640

http://www.freezepage.com/1188061149NJJSVNVRKE

This one is interesting in that it is a HTML screen shot and all the links are clickable

These tool offer excellent ways to archive SERPs as wells Articles

http://www.thumbalizr.com/

this is the homepage link to the first one

http://mashable.com/2007/08/24/web-screenshots/

Here are several more plugins for Firefox – as well as some standalone apps