Some well known and valuable usability resources sifted from the many that are in abundance on the web that you may find interesting.

Useit.com
The home of Jakob Nielsen, the guru of web site usability. Occasionally controversial, always thought provoking and, more often than not, spot on!

Webword.com
Our personal favourite with daily commentary of the world of usability. An excellent resource.

Good Experience
From the consultancy firm Creative Good. Their mission typifies the consumers' desire. Let's make websites that we can all use.

Usable Web
A comprehensive summary of links on usability throughout the world compiled by Keith Instone.

Ask Tog
Another principal of the Nielsen Norman Group (along with Jakob Nielsen). Clear, accurate but entertaining commentary from another industry authority.