I read a post mentioned by Jason Olson and thought it was pretty interesting. One thing that I've been interested in, and plan on looking at in more detail in the future, is an RSS calendaring capability. The basic functionality is already within RSS, but I want to see where RSS would need to be extended to fit more advanced capabilities. I also plan on working with XSL to transform the RSS feed into actual iCalendar events. I haven't looked into this, yet, but plan on it. The project should be pretty simple.
I haven't looked around any to see if this sort of thing has been done before, so I'm assuming that I'll find some good guidance. Either way, let me know if you have any suggestions or know of good places to check out for information. I'll let everyone know what I find out.