Tony Soh at the istockdiary.com blog has been doing some tutorials for the beginning Adobe Illustrator user.
My drawing software of choice has been Adobe Illustrator for several years. I like the fact artwork is scalable. You don't have to worry about enlarging your artwork only to see everything pixelated. Yuck!
It works well with my cartoony style. Even if I am doing something realistic, I usually do the base artwork in Illustrator and export my work to Adobe Photoshop.
If you are an illustrator, I highly recommend Adobe Illustrator.