J Mac wrote:
I want to use a low cost dynamic microphone that I have in
the computer mic in (for learning language) and the one I have
is barely audible with the mic input turned all the way up.

I need a cheap preamp to boost the signal.

Any ideas? I thought surely it was something Radio Shack would
have but I can't find one.

If you're looking for something low cost that will 'just work', rather
than making high-end studio quality recordings, maybe a little
behringer mixer is just the thing for you. The UB502 can be had at
around $30 (new) on eBay (recommended retail price $44,99 USD, assuming
you're in the States).

http://www.behringer.com/UB502/index.cfm?lang=ENG

Before anything though, you may want to make sure you're not
accidentally using the line input of your soundcard instead of the mic
input.