Having spent many an hour agonizing over the minute details of designing and tweaking site maps for various projects, I found Jared M. Spool's recent piece The Site Map: An Information Architecture Cop-Out, particularly interesting.

His basic premise is that if your user base needs to use a site map to find what they want on your site, your design team needs to take a hard look at the root of the problem: usability and information architecture.

It's easy find yourself using site maps as a crutch, but Jared is right -- they're no match for making improvements through usability testing and focus groups.

Without doing a full roll call on every decent usability resource out there, I wanted to call attention to a few that I find particularly useful. Jakob Nielsen's Useit.com is a site dedicated to usability and clean Web design. It's the home to his insightful Alertbox column, which is almost always worth a read.

Gerry McGovern's weekly newsletter New Thinking generally has a few nuggets of good information, and is worth checking out. I've never been to one of his conferences, so I can't vouch for their quality, but his focus on concise writing and clean design is almost always on the mark.

While it's more of an offline resource, I still find Steve Krug's book Don't Make Me Think! (New Riders Press; 2005) an excellent read on the topic of usability. It's a quick read, but once you've read it, you'll probably find yourself referring back to it often. The site for Krug's usability consultancy is Sensible.com.

Another helpful resource is Usability.gov, which is the U.S. government's guide to building usable sites. I don't know why I'm so surprised that a government site on usability is one of the better resources available, but it is. One note -- ironically, much of the site's most valuable information is in the form of PDFs, which is a mark against the site's usability, in my book.