When shopping for lenses, compare lens sharpness using the Lens Image Quality Tool at The-Digital-Picture.com. This tool lets you compare lens sharpness on different cameras at different focal lengths.
Strobist.com is a great place to continue your education about strobes.
Want to peek inside the bag of tons of professional photographers? Shotkit.com is a great place to see what gears the pros use!
Roberto Valenzuela's Books
Roberto Valenzuela has written several insightful books about his photography techniques. He does a great job teaching the reader how to be more thoughtful about posing and light. One of my favorites is "Picture Perfect Posing."