It looks like you already selected a best answer that was given within minutes of asking your question, but here is my opinion.

I would suggest looking at the Rode VideoMic Shotgun Microphone. They have pro as well as a standard version available depending on how much you are looking to spend and how serious you are about getting high quality audio.

The pro version will be a smaller version of the standard VideoMic, and it has also been optimized in many ways. Noise transference is one area that has been reduced using both a revised, shock mounting system and a better cable.

They both have the same basic features as outlined for the Azden model in the other answer here, but ultimately will produce better results due to high end features like the shockmount.

Any of these options are going to blow away the stock mic built into your DSLR, but if you want the highest quality and are serious about audio, I would look into the Magic Lantern Firmware. One of the best features of upgrading to this non-stock firmware is the auto gain control that will get rid of that background noise from the camera that you mentioned. This firmware along with one of the Rode Microphones will give you excellent sound out of a DSLR.