I've been capturing a lot of awesome-quality 1080p video from my 7D, and now I want to step up the sound quality, as the motor is pretty loud and is definitely audible in the recordings. Are there any good mountable shotgun mics that I could get for it? I'd like something that could mount directly on the camera, so I'd be able to keep it fairly portable.
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.
I'm not a video/audio expert, but it looks like something like this has good reviews and mounts to the flash shoe.
Your best bet is to get the mic off the camera and closer to the sound source. If you can't do that at least get an audio recorder to plug the mic into. Your video work will jump by leaps and bounds because of this. The Zoom h4n is brilliant. I've had a half dozen audio recorders over the years and that is the best, and most versatile, for the money.
Though you've already received some great answers, and though I'm no pro, I thought I'd share what I recently learned from speaking to several audio pros at a well-known local shop. If you just buy a shotgun, you'll still need a way to pull audio (I saw that you've already listed the Zoom), check that it's working, mix it, etc. Shotguns will only go so far, so wireless is also an option. Often, both are needed for different occasions. I'm also looking for portability (and have the same camera), so here's a list of recommendations that should help you out:
-Rode NTG-2 Shotgun Mic (kit includes w/SM3 & XLR Cable) - @ $300
-Birnsgear Hot Shoe Adapter - @ $30
-Remote Audio Stereo Output Mini Cable - @ $40
-Hosa Technology Stereo Male-to-Female Mini Y-Cable - @ $5
-Cool-Lux MD-3000 Light and Sound Bracket - @ $27
-Zoom H4n Recorder Kit w/SD Card and Remote - @ 320
-Sony UWP-V1 Wireless Lavalier Mic Package - @ $450
Obviously not all of these items are necessary, but unfortunately, just buying a shotgun mice isn't going to cut it! You'll need at least one windscreen (depending on indoor/outdoor), a device to set highs and lows when recording, etc. We're all still learning what works best (and I'm learning as well), but I do hope this helps. Good luck!