I agree with the suggestions about pencil erasers -- although I wouldn't use the pink ones. I've had the best luck with either the white block erasers or the grey kneadable erasers (HL sells them with art supplies for a few bucks). I use the erasers to get the excess graphite off the fabric (the kneadable erasers are especially good at "absorbing" the graphite) and then use the Tide Stick on any residual marks with cold water. It doesn't always come out 100% with just the Tide Stick, but by using that to pre-treat, it always comes out for me in the wash (I wash in cold water with Tide Free). Definitely make sure the pencil is totally gone before putting it in the dryer.
Here's a link to other options, but so far I've never needed to use them... but if it went through the dryer, these might help. I've given this to parents who already washed/dried their child's school uniform & it worked to get the pencil stains out of their white polo shirts.
http://www.geeksonhome.com/how_65238...il-stains.html