There is a way to rehydrate dry beans without waiting overnight. The downside to this method is that your beans are not necessarily guaranteed to cook as evenly, but that doesn't bother some people.
1. Always rinse your dry beans before you cook them, and take a moment to pick out any poor beans or pebbles that might have slipped through the factory inspection process.
2. Fill a pot with beans and water so that the beans are covered about 2-3 inches by water.
3. Turn the heat up to high and bring to a boil.
4. Let boil for about 2-3 minutes, and remove the pot from heat.
5. Let the beans sit in the hot water for about an hour. (During this hour, prep your onions or whatever you need for the recipe you'd like to use!)
You're ready to go!