Can I use a bluetooth keyboard with Android?
Android natively doesn't support the Bluetooth HID profile which would be required for this. So, your options are limited depending on whether you're rooted or not:
(If rooted): This YouTube video shows the Nexus One connected to a Microsoft Wireless Entertainment Keyboard 7000.
(If not rooted): Teksoft provide a Bluetooth HID driver (commercially, costs about 10 Euros), which is reportedly successful.
Note: Individual devices that run Android may have the HID profile added by their manufacturer -- for example, the Dell Streak supports Bluetooth keyboards.
Android 3.0+ supports several bluetooth keyboards such as the Logitech Tablet Keyboard, which I use successfully with my Android 4.0 phone (not tablet) for note-taking and IM.