The place where you can get information about gem dependencies, study their family tree and even build own graphs form your Gemfile.
Lately, I’ve been looking for various libraries for 3rd party integration to facebook, linkedin, etc, and unlike some areas of ruby gems (web framework = rails/sinatra), there are no clear cut winner that’s a head and shoulder above the rest
So that requires me digging around rubygems and github to find a viable candidate, not just to use, but to contribute to. Sometimes, I would find a great underlying library, like Typheous and wonder what other libraries are using it.
I had a commandline tool that answered that question, but it was slow, since it had to index the gemlist. And plus, I forgot what the command is now.
Behold! Enter GemFamily. This is great because I can look up “what gems depend on this gem?” and see if those libraries are also awesome.