I find your question doesn't make sense. Sharepoint has modules for message boards, calendars, document repositories, and work flows that can be structured. Each site/subsite is unique based upon client/department/personal. "Office collaboration" just sounds like buzz to me.
Sorry, but, uh, QFT. Everything you mention is built into the standard Windows Sharepoint Services 3.0 install. There are no add-ons (aka, WebParts) needed to accomplish those things.
Beyond that, however, there are a lot of things out there. On our regional sharepoint site that I've been working with since this past spring, I've added a few web parts to have the "Daily Dilbert" comic strip automagically be included on our IT site, a weather web part that shows weather conditions for the areas you specify, and a few other minor things to just enhance the features that are already there. One solution we are currently looking at is a Charts and Gauges tool that lets you have pretty neat graphical representations of data that exists in either an Excel spreadsheet or a database (
http://dundas.com/).
Oh, and I took it upon myself to get familiar with the Google Maps API to code an inter-office driving direction page so the folks who travel to different offices can easily get the directions they need without having to know the address of where they're going. But that's just putting some regular HTML/JavaScript into the Content Editor web part that is part of the default install of WSS 3.0.
Is that what you're after?