A lot of content on the web is split into numbered pages. AutoPager is a Firefox extension which concatenates pages, so instead of clicking "next page" links I can simply scroll down. This is great, and it makes me realize how obsolete pages are on the web.
In the past, I've used CustomizeGoogle to "stream search result pages". That was pretty good, but it sometimes got stuck in a loop when I was logged in and it only supports this feature for Google. AutoPager supports it on many web sites, and I have not had any problems with it.
A few suggestions: The simple modal prompt is annoying, so turn that off. A green rectangle in the bottom right corner of the screen is much nicer than a "yes/no" popup. I generally set AutoPager to only autoload one page. Page loading is so fast, that by the time I'm done with that page, the next page will be loaded and so on.