Check out the application 'Voice Recorder'. It's free and has a home screen widget. It records in native recording format for phones though, so you'll eventually need a converter to convert the file if you need to transfer it to your computer. This is the app I currently use and it works great.
There's another pay app that I've been considering getting that records in a .wav format which is already computer ready. Been thinking about spending a few bucks and getting that. I'll post the name momentarily.