That's my Second Life avatar with Catalina the Library Cat at the reference desk on Info Island. Like Scratch, Second Life is great way to get into scripting, experiment with and share ideas. There are lots of library projects to see and librarians to chat to (if you follow US time).
A lot of people are initially underwhelmed by Second Life. The graphics aren't up there with the latest x-box game, the interface is clunky and it takes some time and effort to create stuff or even edit your appearance. The great thing is that you are able to create the environment around you and define the rules that govern it in collaboration with other residents. So it's more like a big 3-D wiki than a traditional computer game or social networking site. The gratification comes from the effort you put in. Want to see a 3-D OPAC that delivers ebooks and streams audio books directly to you. Head to Info Island, find some like minded people and start scripting.

Here's a review to some recent Second Life innovative locations:
http://secondlife.com/destinations/lindenprize