This was one that has been bugging me for quite some time. I use Google Calendar for everything I do. However, like so many others the corporate world ties us to Lotus Notes.

Luckily for us the Open Source community comes through. The "Lotus Notes to Google Synchronizer" is still currently in the Beta and has some flaws but right now its the best option I've seen.

http://lngooglecalsync.sourceforge.net/