AutoPager

AutoPager automatically loads next pages when you reach the end of a page. It works on a ton of sites,Google,Yahoo..
It works well with most other add-ons adblock plus, WOT and most of the greasemonkey scripts.
You can also try AutoPagerLite.

----------

Firefox 26 compatiable version here:
https://secure.teesoft.info/autopager/autopager_0.8.0.10.xpi

(Please use Lite mode if your device has less memory or low processor.)
The AutoPager Firefox extension automatically loads the next page of a site inline when you reach the end of the current page for infinite scrolling of content.
It includes a adblock similar features to allow you filter out the ads from the contents in the loaded page contents.
It works well with most of the greasemonkey scripts.
By default AutoPager works with a ton of sites, including Lifehacker, the New York Times, Digg, and, of course, Google. If you want to add your own custom autopaging to unsupported sites, the site wizard feature makes it easy (first pick the Next link, then pick only the content you want loaded. The site workshop provide more features like auto discovery the links and content.
It's configuration is base on XPath. You can find there is a built in function to create a XPath by click some links on the pages. This extension will import online configuration from this sources,these configurations includes support for some widely used sites and some general support for forums.
You can also share your site rules by click public button in the setting dialog.
You can find XPath tutorials at http://www.w3schools.com/xpath/ and http://www.zvon.org/xxl/XPathTutorial/General/examples.html.
You can always get the stable version here and the newer develop version at: http://www.teesoft.info/content/view/68/1/

You can find our tutorials at http://www.teesoft.info/content/view/91/1/
And some tips for creating AutoPager rules for new sites:
http://www.teesoft.info/content/view/87/1/
It also supports show the related searches for the page. You can turn it on with the choose the search engine you want.
AP doesn't enable related search unless user choose a engine from : Surf Canyon Search, Google search, Bing search or wikipedia. Other search engines are being working on.