I think the most obvious already is Bitcoin, disrupting payment services. Being the "first to market" is obviously its biggest advantage right now.
Monero
Monero offers anonymity, so I can see its uses eventually taking some of Bitcoin's market share.
Ripple
Ripple has a great chance of offering a high value of disruption because of its adoption by some banks already.
Golem
Golem is really unique in providing decentralized supercomputing power. I need to find out more how much value it can add, but supercomputing on someone else's power bill and hardware can offer a lot of computer power!
I'm still learning about block chain technologies and what powers they have to disrupt industries, so I would love to hear about other ones you think are interesting.