I've had the good fortune to stumble across The Ruby Toolbox.
This delightful site is filled with collections of helpful, nifty plugins and gems that help make the life of any Ruby and/or Rails developer much more pleasant. There are some 75+ different categories that deal with ActiveRecord, Backups, Code Metrics, CSS Frameworks, E-Commerce, Game Libraries, Gem Creation, and on, and on.
Not only are projects, gems & plugins listed, but they are rated in terms of how much attention the project is receiving. The most popular projects are listed at the top with an attractive scale along side to the right to help you compare the popularity of different options.
If you're doing Ruby and/or Rails development and haven't visited this site, then you really deserve to do yourself a favor. I'm headed there now!