I've found a couple nifty tools that I figured I'd share:
Rak is a grep replacement written in ruby - it has some pretty neat features including nicer output by default, ignoring .svn and other similar directories. Definitely worth poking through at least the info on the website.
Reggy is a very simple, but useful OS X app to visually test/construct regular expressions. It's super simple and doesn't do anything fancy, which is why it's nice.
Hexpicker - an OS X color picker plugin, it just adds another tab to the color picker that shows the hex code of the color selected. This makes it easy to grab the hex of any color on your screen. T
his isn't a utility of any sort, but the RubyConf Talks are online, free. If you missed out, go watch them!
