I hate to chime in and be the "Burton Brand whore" here, but this pack has served me well over the last year:
Burton - AK 20L Pack (Roasted Brown Smoke Camo) - 6PM.com
Not that exact one, but its very similar. Has three pockets: One main large one, a zippered small one within the large one, and an outer pocket. The outer pocket is pretty water proof, and the large inner one only got water in it once when I didn't screw the tube in correctly :P
I use the small pocket to carry my board lock and tissues, the large one to carry a small stick of rub-on wax, a screwdriver, snacks if I have any, and the outer pocket to carry extra gloves or a neck warmer.
It won't carry more than, say, a long sleeve T, folded, BUT the pack is very compact and light weight... its probably only 3" thick, and it carries my BOARD if I wanna hike backcountry!!
The only downside is that the water will freeze in the drinking tube, so after a few sips, just 'blow' back into the tube to clear the water out and you're good to go