While a TodoList app is not suited to ethereum-based backends, I originally wanted to do one to get my hands on this technology and to have a very simple app actually doing something I am familiar with as a front-end developer.
You must run a node on your computer, whether its a real or virtual one. For development speed reasons, the best choice is to use testrpc because you have as much ether as you want and don't need to mine transactions.
sudo npm install -g ethereumjs-testrpcsudo npm install -g truffle
npm install
In a terminal (or in vagrant ssh on Windows, see above), run testrpc