iUseThis is a new site which can be best described as an union between digg and MacUpdate. The front page of the site displays a listing of the most recent updates for OS X software. Registered users can click on the applications they use to, in a sense "voting" for them. The more people using an application, the higher up on the page it is. This lets visitors easily see the most popular software releases at a glance.
iUseThis also has the handy feature of storing a list of the applications you use, providing a quick reference if you ever need to re-populate your Applications folder. The developers of the site are also working on an "advanced" recommendation engine that will suggest new applications based on what you currently use.
Despite the seemingly complex nature of this idea, its really quite simple when you play with it, and could turn out to be quite cool.