Intrusion Detection is in my eyes one of the hottest topics in IT Security at the moment.
I did myself do some work in the area. The first thing which unfortunately I can not disclose was a LogAnalyzer written in Java that you can run on any logfile and define rules to process the logs.
The even more interesting work was THOR. I am right now about to write a research paper about it and publish it on a security conference. Meanwhile there is my Thesis report which is downloadable online!
And one last project of myself related to IDS is Odin. It's about a Switzerland-wide Intrusion Detection System. The project is just about to be defined and launched. Not a lot there yet, but this should soon change!