Non-Drupal inspirations for research and learning

I've just come across the fantastic software for social bookmarking for academics Connotea (see http://www.connotea.org) and started thinking about the many great projects out there which we could either learn from or integrate into Drupal. Of course, there are some obvious candidates such as Moodle, Elgg, Gallery2 that we all know about. But what about services such as Shelfari or LibraryThing? So I thought I'd start a thread where we could talk about what others are doing and how we can benefit from their hard work.

As I said, my first recommendation for something that deserves a serious look is Connotea which is directed straight at the needs of researchers and does a great job of integrating with library services. Its one advantage over Drupal with Biblio is that it stores all resources (links and bibliography) as sharable links (del.icio.us style) and can export them into a reference manager. This is also a bit of a disadvantage because it can only sort by tag and not by author, year and other things like Biblio can. Still, I found its flexibility and versatility to be extremely useful on a recent project. I used Connotea (http://www.connotea.org/user/dominiklukes) for data collection and then exported them into a Drupal site using Biblio for presentation purposes. Of course, my preferred way would have been to do both in Drupal but this did work pretty well.

Any other suggestions for software we could benefit from?