Sea turtles, they do not make good pets. They need an enormous amount of space, and just keeping all that water clean must be a nearly full time job. (I refuse to keep even a small aquarium.)
Plus, it is illegal to keep sea turtles as pets.
Still, there are a few ways to adopt a sea turtle, and ehow describes some of them for us, just in time for Christmas. The adoption site is AdoptASeaTurtle.com.
Disclaimer: I have not tried this, nor have I checked out the organization in any way. But it sure does sound neat.