Yesterday I got an invite for a service called Freebase. Here’s what they are about (from their FAQ):
Freebase.com is home to a global knowledge base: a structured, searchable, writeable and editable database built by a community of contributors, and open to everyone. It could be described as a data commons. Freebase.com is enabled by the technology of Metaweb, which is described at www.metaweb.com.
After some time playing with it, I’m quite impressed. While the service is mainly geared toward developers, it’s actually quite fun spending some time tweaking entries and adding new ones. They are still invite only, and some entries reflect that (many entries still rely solely on the content added by their crawler from sites licensed under the Creative Commons license), but I do have a feeling they could find a pretty dedicated community once they open up.