In I Use This, applications are tagged by their function (utility, iTunes, video, web, etc.) and registered users click to note “i use this” for the applications they use. This democratic way to rate apps, by counting the number of users of the application can provide more meaningful result about the value and popularity of an application compared with simply using ratings submitted by users like in Digg.
Users are required to register in iusethis which allows them to store the apps they use on iusethis. The software can be downloaded again as and when needed. By registering, users can join in the community too to help others pick the best apps, or get the recommendations and suggestion to new apps based on your profile. However, only application owners can add tags to the applications they submitted.
IUseThis is a great way to discovering what other Apple Mac OS X computer users are using. You can try it out here.
Update: Windows and iPhone versions are now available.