Lately I've been working on my Adobe Illustrator chops. It's been a long time since I've worked with it, currently most everything I do is raster image based.
One great thing about the abundance of information on the internet is that you can learn just about anything. So I've been working on learning all the Illustrator tricks and tips I can.
Certain things (i.e. the pen tool) have made me cringe for far too long and I decided to search the internet for tutorials, tricks and tips, which there are plenty of. Below I'm listing some of my favorite sites and/or compilations for tutorials. If you have any favorites that I've overlooked please let me know in the comments.
Slick Tutorials: Illustrator
and a couple lists:
Smashing Magazines Adobe Illustrator Tutorials - Best Of
InstantShift - 125+ Ultimate Round-Up of Illustrator Tutorials