Pegged jeans are jeans taken in until they are excessively tapered. Done right, it's just possible to get one's foot through the bottom. If you gain weight, you'll have to throw them out.
Pegged jeans are usually dark blue or black. The former is more traditional, but the latter is more common on young Hollywood punks of today. Polyester pants, like Levi's Action Slacks, also look good pegged.
Although pegging jeans is traditionally a DIY project, it is now possible to buy jeans already pegged in the mall.