HTML5 ICON File Format: SVG
Documentation Icons consists of 12 high quality, free icons in these sizes: 64x64px in PNG, AI and EPS file formats.
Case Icon Free Vector Graphic
File Format: Ai, EPS, JPG
Glossy Vector Icons Part 2
Glossy Vector Icons
I usually try online photoshop and illustrator tutorials which is written by graphic designers. They are very useful to improve your skills.
Recycle Button Free Vector Graphic
Networking Free Vector Icons
Green Collection Free Vector Icons