Glazed Lists is a clever Java API for list filtering. The swing intergration is particularly nice, and they even have a nice JNLP demo that works on live data from real projects rather than a canned fake like most JNLP demos. For example, the Glazed Lists data is the list of issues for the product itself. Great job!
I wish more demos were as realistic (and performant) as this one. To be honest, the demo is so excellent (look at the bug list for Looking Glass Core) it overshadows Glazed Lists. But this is a such a plus: an utility API should never get in the way of the GUI frontend, and Glazed Lists lives up to that expectation greatly.