Both focus on more than website design, but they helped me understand how users interact with my user interfaces. I'm sure there are also a ton of great blog posts out there too, but I found these books the most helpful.
http://www.amazon.com/Emotional-Design-Love-Everyday-Things/...
Designing Interactions
http://www.amazon.com/Designing-Interactions-Bill-Moggridge/...
He passed away in 2012. I wish someone wrote a worth revised edition.