Roughly said, you get the more bittering out of hops the longer you boil them, and more aroma the less you boil. Therefore, you typically get bitter between 60-30 minutes, flavor between 30-15 minutes, and aroma between 15-0 minutes. If you use an IBU calculator you'll see that you still get bitterness from even a 5 minute addition, but it's much much less than a 60 minute.
Very few hops are considered good for bittering only, since even the most popular bittering hops still bring some flavors and aromatics to the table. For those of us on a budget, it's also important to get the most out of our high-AA hops and not waste them on flavor/aroma.