Dragon Dictation: A free dictation app that'll convert just about anything you say into text, and send it to a wide variety of application on your phone, including your email and texting clients. It helps that it's based on what is probably the most competent speech recognition engine on the market.. Oh—and that it's totally free, for now.

Note: By default, this app uploads some of your contact info to its makers' servers. As far as I can tell it's just the contact's names, so that they can be processed and filed away for recognition later.