When Macworld's Christopher Breen got back from the MacMania/Photoshop Fling cruise, he was inspired to clean the sensor of this Nikon D70 himself. He carefully weighed the options (and advises you to, as well) and bought an Econo 1.6x Complete cleaning kit for about $250. In his article, he walks us through every step of the process.
Again, you need to carefully consider the costs and risks involved, but if you do decide to clean your own sensor, his blow-by-blow account is a good place to start.
