The SDK version of Android 3.0 Honeycomb has been ported successfully to Google Nexus One. Dubbed as Honeycomb N1 alpha v0.1, this tablet-optimized version of Android will bring all the goodness from the latest and greatest version of Android to Nexus One.
If you are feeling adventurous, you can give Android 3.0 Honeycomb a go on your Nexus One. Beware though as not everything is said to be working. Installation instructions, and download links can be found at the XDA-Developers forum here.