Most kids like to draw. I've found we've gotten a lot of use out of "how to draw" books. These get used over and over again. While crayons are less "pokey", and therefore better for little kids, colored pencils give older children more freedom in their drawing.

We usually stock up once a year - in August or September, when all the school sales are on. We'll buy 20 or more little boxes of crayons, tons of colored pencils, etc. I store the supplies and bring a new box out every month or so. Target, Office Depot, Costoc, even computer stores like Frye's, will offer great deals on these items. I've also found that Office Depot usually has very good prices on crayons all year round. Discount drug super-stores will also have sales on these items from time to time.