Your probably looking for some working examples of dApps (decentralized apps). Install MetaMask for Chrome and visit one of these sites: http://etheroll.com, http://etherdelta.github.io, and http://oasisdex.com are all working examples of smart contracts at work.

>I'm just learning but are there any real world examples of this yet?

Yes. The whitepaper lists many potential applications [0]. Some interesting ones today include issuing tokens for crowdsales ("ICO"s), gambling applications (FunFair), distributed computing (Golem), peer-to-peer payments and distributed apps (Status). There are many more that I am not familiar with.

>any idea what % of transactions utilize this today?

https://etherscan.io/accounts/c lists all smart contracts along with the amount of ETH they hold and the number of transactions that have called them. This doesn't completely answer your question, sorry.

[0] - https://github.com/ethereum/wiki/wiki/White-Paper#applicatio...