Taxis are too expensive, but there are several shuttles/busses that go to the Disneyland area.
The Disneyland Resort Express is a bus (run by Gray Line) that picks people up about every 1/2 hour or so (depending on the day). There is also SuperShuttle, and there is Primetime Shuttle. The other shuttles are not as well known, so I wouldn't recommend them. I'm not saying that they are bad, just that we don't know too much about them.
There is also Karmel Shuttles we have used them a few times and have really liked them. They were always on time and very nice. I would definitely use them again.