You can register domains in the .id namespace currently. Domains in the .id namespace are called Blockstack IDs as they're meant for people. Soon there will be other Top-Level Domains (TLDs) on Blockstack, and you'll be able to register domains there as well. You can create your own namespace/TLD as well. It's a completely decentralized system.
Maybe we need a different color for hyperlinks? CC: @guylepage3