People keep asking about my microphone that I use for podcasts. Let me post it here once for everyone (including Roland Tanglao, who says no one is telling him what mike to use). I use a modest Radio Shack mike, 33-3004 is the number. It costs $40, and you can see if they are in stock in your area. I've had it for nearly 10 years and it continues to work like a champ without incident.

I also run that through my cheap Radio Shack mixer to do the role of a pre-amp. The signal straight from this mike isn't strong enough for the iMic input. This is a unidirectional mike, which is imporant because you don't want it picking up all the room noise, just you. Make sure it is oriented so that all the noisy computers and crap are behind it, and it will help a lot. Be sure and spring for the extra $2.99 to buy the foam windscreen, aka "clown nose", to put over the wire mesh. It makes a world of difference for a negligible amount of money.

Update: Roland asks the follow-on question, what mixer am I using? I'm using the Radio Shack SSM-60, SKU 32-1214. Looks like they don't carry that anymore because searching on that item number brings up user manuals but no way to buy it. The closest equivalent I see is this thing. You could maybe use a mike pre-amp but the advantage of buying the cheap mixer is that if you get another mike or external source you want to pipe in, you can do that all in hardware with the mixer. The downside is the lack of portability. I've been happy with all my cheap microphones and my cheap mixer for a very long time.