Do commercial aircraft have electrical outlets?
Several of the answers here seem to suggest that this only happens in first or business class. While that was historically true, it's not so true anymore. Airlines such as Cathay Pacific and Korean Air, for instance, have them at every seat in most (or all?) of their long-haul aircraft. Delta also has it in parts of economy on several of their long-haul configurations as well as in all of economy on their recently-acquired 717s and 737-900ERs. You can check with your specific airline or with sites like Seat Guru before booking to determine what is available on any given aircraft and at which seats.

As Lnafziger said, some airlines' systems require adapters, while others don't. At least from personal experience, it seems that most of the recent ones do not. On Korean Air, Cathay, and Delta, the plugs are designed to be able to fit any of the standard power plug types (e.g. North American, European, Asian, etc.) Since most new electronic devices use auto-switching power supplies, they should accept the 110V/60Hz supplied by most of these systems, even if they're designed for 220V/50Hz markets.

Here's a picture of one of the outlets in economy on the Delta 717s. Notice that the holes are cut such that any of the standard plug types will fit in it. The slot on the bottom is a USB power port.