Here's another new event planning site that I just came across. It's called PLUQ. I found this article about it that spells out its various features. It seems to be similar to some other event planning sites, but this one is geared for casual use, for parties, dinners, and such, with lots of interactivity possible.
(Update: 2/24/09: here's another article that describes the difference in PLUQ as compared to other event planning sites, and how it's more interactive.)
And if you're looking for a speaker for an event, you may want to check out the SpeakerSite.com. You can search for speakers by topic, post an "open call" for a speaker, or have the folks at the site find a speaker for you.
Have fun exporing!