Resto shamans are awesome healers at 70.
In my opinion they are the best heroic healer simply because chain heal is so powerful.
Resto shamans also usually find a place on most 5v5 arena teams as the 2nd healer, although this will depend on the rest of the team composition.
Enhance shamans can do some very nice DPS and are a great addition to any party with a warrior tank and a rogue as DPS.
If you can find some friends, try and find a good warrior tank, a good rogue, a good mage, and a good healer (class really doesn't matter) and you will be set to run as many heroics as you want.