Any time I feel I need some inspiration, I always go back and watch this video. There are so many good tips on it... slide, tone, vibrato, bends, note selection. If you are into any type of blues or blues/rock, check this one out.
http://www.amazon.com/Warren-Haynes...5&sr=8-2&keywords=warren+haynes+instructional
If you want something a little more insane... speed, warmups, tempo, technique... check out the insanity:
http://www.amazon.com/John-Petrucci...1&sr=1-1&keywords=john+petrucci+instructional
I have almost all of the Guitar Grimoire series of books as well... tons of fun stuff if you have the time and patients to dig into it or want to learn some theory.
Hope it helps!