It's been pretty amazing to see how our own Clearspace deployment inside Jive Software has improved communication and helped us get work done faster. We're all Clearspace addicts, and as such, some of our fun has moved there. A few examples:
Somehow, a mustache growing contest took off inside the company. Several blog entries with pictures made it into the "Water Cooler" space, including an embarrassing attempt by me. The clear winner was Todd (who will not be pleased about me posting his winning entry).
There are lots of avid runners at Jive and group runs and races are all getting discussed through Clearspace.
Erskine's personal blog entry about his nerd score (59) attracted a huge number of comments from all over the company. Others' scores ranged from 6 to a perfect 100.
Everyone controls their own avatars. The ability to inject a bit of personality into Clearspace has proven to be a major incentive to participate.
We even added a Youtube macro to Clearspace recently, which makes it easier to share the occasional fun video.