I bought a Blue Snowball microphone to help me try out dictation. The version I bought has both cardioid and omnidirectional settings. Cardioid means it only picks up sound from in front of it. This means that you can possibly use it even if there's other noise in the room. Omnidirectional means it picks up sound all around it. This means you can even walk around a bit and talk and it’ll hear you.
I am writing up this DW entry right now using the new microphone + Google Docs voice recognition, and it seems to be working pretty well. I'm walking around as I do it. I have to correct a LOT of mistakes, so I’m going to eventually try out Dragon Naturally Speaking to make this go more smoothly, but for now this is not bad.