I've been crazy busy for a while, but what little spare time I have grabbed here and there has been used investigating some areas of Rails I hadn't played with before, like route globbing and running without a database. The results are a couple of tools, one useful, one most definitely not.
The first (and most useful) is "Has My Gem Built Yet?". I have a bunch of ruby gems on GitHub and get annoyed that I have to keep running "gem update" while waiting for GitHub to build the gem once I've pushed the code. Well, no more. Just put in the details, and the page checks for you and pops up a message when the gem is done. Nice. It got picked up on the GitHub blog, and I've even had some patches sent in. It's a nice feeling :)
The second app is somewhat less useful (though still entertaining). After a suggestion on Twitter by Tom Taylor, I built a website which lets you bookmark sandwich combinations. There are a couple of interesting bits in this though - first is route globbing, which is the Rails way of using arbitrary bits of the URL as parameters to an action. Not something you use in every project, but still. More importantly, I've used it to test out rubymarks, a Rails plugin for generating links for social bookmarking services.
I love Rails for this sort of thing. I can't think of other system I've used that would let me create such fun things in the tiny snippets of spare time I have at the moment. And of course, everything above is open source and available on Github.