Check out the EverNote Windows Mobile technology preview

Some of the great features in the Windows Mobile client include the ability to create notes on your device with your stylus (OneNote only lets you create text notes), take snapshots with your mobile device camera and save the image as a note, record audio notes, and search through text notes. There is not yet any syncing capability in this preview so you will have to manually copy databases back and forth between your device and PC, but I imagine there will be conduit once the software is released as a full product. There are some other known limitations as you can see on the bottom of the technology preview site so keep these in mind as you try the product too. I think this is a great step forward for mobile productivity and look forward to further developments.