I think that Ryan Raaum’s Locomotive is about the best thing since sliced bread. It lets you really easily set up any number of Rails applications on your Mac, and manage them really easily. Remember to make it one of your Login Items and check all of the applications you want to run, and your Mac becomes a really useful group application server on your home network, for free. About the only thing you need to do yourself is create the database for your application, which is really easy with a tool like YourSQL.
Why would I do this? For one thing, there are lots of great applications written in Rails already, free to download and use. We have to keep minutes for our work meetings, and those have to happen at least every week. So we just enter them into our blogging app here (Typo, which is awesome), give the post a few tags, and we are done. Convenient to enter, easy to search, quick to print out, and because it’s not on the Internet at large, it’s secure. We can get to it from any desktop or laptop in the house.
For another thing, there is no easier platform for developing a useful application quickly around today than Rails. I am not kidding you. I am not a programmer by trade, and I have only been learning Rails (and Ruby) for less than a year, and I built a simple issue tracking system last night. And we are using it today to track issues for Ladybug and other applications we are working on. Hell yeah I am happy about this!
Let me put it this way. Let me elaborate on that last point. The only real free alternatives to my quick-and-dirty issue tracking program that I would consider not only have far more features than I want, but they can be incredibly difficult to install. I would say, in all honesty, that it was faster to write this app in Rails than it would have been to install Trac on my Mac. A lot more fun, too.