I did look at the Oracle Collab suite, and I have heard good things about it.... but it's WAY WAY overkill for us. To get the calendar you have to get either the Unified Messaging package or the full Collaboration Suite, both of which include other stuff we just don't need.

Even as a complete solution, either package is too much for our 35 person org. Maybe if we were 10x that, and more tech-oriented, it'd be up our alley.