[img src="" caption="" credit="" alt=""]
Alexaholic, the service for comparing the success of websites using Alexa's tracking, hasn't had an easy time. But the idea lives on in the form of Appaholic, a totally separate project that lets you enter the names of Facebook apps and compare their popularity.
It's extremely useful if you're developing one of these things, and interesting to use even if you're not (see if you can spot the spelling mistake on the homepage). I assume they're scraping this data, though, so a ban is possible if Facebook is feeling nasty.
Update: turns out there's also Appsaholic (with an "s"), which provides a text-based interface and user counts for apps.
Related: Statsaholic lawsuit