Sans our very orange (tanned?) hands in the photo above, I give chalkboard nails a big A+. Cousin A brought a kit to Colorado and one night we dolled up our fingernails. As the directions instruct, you paint on two coats of the black, matte, chalkboard polish. Then, once the polish is dry (which takes about a minute), you break out the bright-colored chalkboard markers and doodle to your heart's content on your nail surface. The final step is a coat of clear nail polish and voila, chalkboard nails!
Cousin A bought her kit at Sephora ($25). If you follow this link, you can see the kit - the markers and polish I described. I also just spied this DIY tutorial for chalkboard nails in case you want to use supplies you might already own.
I pretty much love anything chalkboard and being a teacher, well, this is just my style!