It would look something like:

contract Hello { string greeting; function setName(string name) { greeting="Hello "+name; } }

The solidity compiler will automatically produce a "getter" function to retrieve the greeting.

Yep.

Running it is about as far as I got with my investigations.

https://www.ethereum.org/greeter

SimpleStorage is one of the 'HelloWorld' equivalents of DAPPs.

http://solidity.readthedocs.org/en/latest/introduction-to-sm...

Third party oracle services are provided by Oraclize.it

I think the most logical DAC should be a distributed network of lemonade stand franchises :)