I learned about Eventful through Webware 100's 2007 awards site. First, the good news... Eventful looks like an up and coming tool for people to learn about special events in their area. Also, it is a great way for non-profit organizations such as libraries to publicize their events. In addition, several organizations are using the site to publicize specific volunteer opportunities. On the negative side, the search function needs some tweaking. I was surprised to find that Eventful does not support search by zip code. You must match the city name exactly. I live in Broward County where there are 30+ cities in one county. I don't want to have to guess that a performance is going to take place in Sunrise or Fort Lauderdale, Florida. A proximity search by location would really help out here.
Update: Brian Dear from Eventful contacted me with some helpful information on how to use the proximity search in Eventful (See his comments). After taking a closer look at the web site, I recommend using the Advanced Search for conducting proximity searches.