WebShot allows you to take screenshots of web pages and save them as full sized images or thumbnails. Screenshots images can be output in the JPG, GIF, PNG, or BMP formats.
The freeware version comes with a demo of the command line interface, which can be purchased, and used to streamline the screenshot process on whole websites. The server edition of WebShot comes with a DLL that will allow you to embed WebShot technology in your own applications.
Download: WebShot 1.76