Usability Resources Online

Usability Basics

UsabilityFirst
An overview of usability along with tips and recommendations.
About Usability (UPA - Usability Professional's Association) Good information regarding the basics of usability and user centered design.

Usability and User Experience (Society of Technical Communication)
If you are new to usability, these articles and other resources will help you get started.
Digital Web Magazine
A collection of good usability articles
User Interface Engineering
Information architecture articles
Web Usability and Navigation
by Merlyn Holmes, A beginners guide to usability engineering
Don't Make Me Think
Excellent book by Steve Krug

Usability.gov (This is an official U.S. Government Web site managed by the U.S. Department of Health & Human Services.)
Tips, articles, and links covering usability guidelines, methods, news.
UsableWeb
A collection of links about usability and user interface design. A bit outdated but still some good information can be found here.
UsabilityNet
Comprehensive resource site from the European Union.
UseIt.com
Jakob Nielsen's Usability Columns
Guide to Usability Engineering Resources (University of Maryland)
A guide to usability engineering web resources
Usability Toolkit (Society for Technical Communication)
The Usability Toolkit is a collection of forms, checklists and other useful documents for conducting usability tests and user interviews.

Usability.gov Usability Guidelines
Research-based web usability guidelines developed by the US Department of Health & Human Services
Top 10 Design Mistakes of 2005 (Jakob Nielsen)