If you've mastered the basics of Adobe Illustrator (and/or other vector graphics programs such as Inkscape), and you want to add some new tricks to your repertoire, check out Vectortuts+. This site is an awesome resource full of tips, tutorials, articles, and assignments shared by artists from across the internet. Vectortuts+ is part of the hugely popular Tuts+ Network, an online learning platform which provides free content to help teach creative skills. Tuts+ sites also offer premium accounts with access to e-courses and e-books for a fee to those wanting more in-depth information.
I spent some time trolling the Vectortuts+ archive and found several tutorials that might interest surface pattern designers. Have a look and then explore the site to see what else you can learn. Enjoy!