I love Craigslist. I like to consider myself a Craigslist power user. What I like to do is perform a search on Craigslist for terms I'm interested in and then put the RSS into my feed reader.

Example: I'm currently searching for a hip-hop group to play drums with. I search the musician classifieds for the terms "hip hop drummer", then subscribe to the feed into Google Reader and now, whenever someone posts to the musician classifieds with the terms I specify, it shows up when I check my feeds.

This technique is also helpful when I'm trying to find a used instrument or piece of computer hardware and I have a price point I want to meet. You can, for example, find all the MacBook Pros under $1500.