Recently I started buying and selling domain names and I think there is a lot of opportunities to make money there. You can register domain names using Bitcoin on Namecheap and it's super easy, just be careful not to get overenthusiastic, most domain names people buy and think are awesome are actually worthless. You need to do some research before you invest.
It also helps if you can put up a mini site or some content and start driving some traffic. Selling a domain that already has traffic is always worth more than a domain with just a "cool name". Obviously there are some exceptions, but finding a name that is highly desired by someone else is no easy trick.
Yeah I don't think there's much money to be made here unless you get really lucky and all the good ones are already taken. I see plenty of people trying to sell their domains asking ridic prices and nobody ever buys them. There's so many domain extensions these days that you can always just purchase a different one any way.