CompanionLink for Google Calendar™ is a two-way synchronization solution for people that want to extend their Google Calendar onto their desktop calendar systems or mobile devices. It can synchronize Google Calendar with all the latest Pocket PC, Windows Mobile, Palm, and BlackBerry devices in addition to Outlook, Lotus Notes, Palm Desktop, and Groupwise applications.
Make changes to your calendar from any device or desktop program and rest assured that your Google Calendar will be updated automatically the next time you sync. Whether you’re in the office, at home or on the road, you can now have the power of Google Calendar at your fingertips.
It works with all Palm, PocketPC/WinMob and Blackberry devices, as well as with Outlook, Notes, and Groupwise.
There are a few caveats, basically because Google Calendar is still in beta and the APIs are adjusting. Once the bugs shake out, though, I seriously have to take a look at this.