Massive Voodoo has a nice essay on keeping your brushes clean.
Anatoli’s Game Room has a tutorial on painting 15mm horses.
Kevin’s Miniatures and Hobby Table has a photo tutorial on painting a Games Workshop Lord of the Rings dwarf.
The Man Cave has an article on painting rust effects. Lots of good techniques here.
The Leadhead has a very nice article on getting started in airbrushing. Well worth the read.