Looking at the manual which you can get from here, for the HC18E
http://www.sonydigital-link.com/manu...nuals.asp?l=en
Page 101, item 13 is external MIC input. (Note, for some reason the manual is only in Italian and Greek, I don't speak either, but I believe "microfono esterno" is "external microphone".
Now, having been given some birthday money by my in-laws, I'm looking to get a external mic myself. There are loads of different types of mics, depending what you want to do. For instance if you are filming interviews, you might want a mic the subject can attach to their lapel.
If you want something mounted on the camcorder, probably a "shotgun" mic is best; this is what I am looking at. They are directional, so they will pick up (more) of what the camcorder is pointed at; little to the side or behind. This is useful for general use, and should be better than the built in mic (which are generally considered to be poor by audio experts).
I'm thinking of the Rode VideoMic; a review here:
http://www.sundancemediagroup.com/ar...e_VideoMic.htm
Cheapest I've found is £82, delivered.
I value the opinion of the review author; he's an expert video editor and has done a lot of audio work. I own one of his books...
In terms of "shoes" - the shoe is that little bracket on the top, where you can attach a light or a microphone mount. The mic above will work on any camcorder with that standard "shoe". Some require special power or connection from the shoe and will only work with a certain model.
Mark