Recommendations for an External Microphone?

I recently purchased a Canon T4i and I'm looking for recommendations for an external microphone.  The Shotgun type appeals to me the most, because of it's portability.  I'd rather have it attached to the camera so that it moves with me.  I really don't plan on doing interviews, so I don't need one to place on a desk near the camera.  The final criteria is the old money factor.  I'm looking for something relatively inexpensive, but I also don't want to waste money on something that won't do the job much better than the two internal microphones on the camera.  I also don't want to break the bank buying a product that is overkill for my needs.

Thanks in advance for any advice that you might have.

Frank