What is Dabble.in? [Updated]

This morning, Twitter was awash with messages reading: "I just reserved my Dabble.in username. Gets yours here." My friend Burt Lum posted the first tweet I saw, and as an obsessive signer-upper, I raced over to register. My post sparked another half a dozen of my friends to sign up and tweet as well.

But many also asked, "What is Dabble?"

After all, the …