Mist recently launched its Beta (0.8.0), you can call any website for getting the HTML and JS files. What happens if inside my Dapp I make a XMLHttpRequest?
In addition to what eth was saying, and for others coming here through google: I had the same struggles in the beginning. I didn't really know where to start. What helped a lot was reading through the solidity docs, there are some good examples in the beginning of what is possible with Solidity and what not.
As a starter: https://solidity.readthedocs.io/en/latest/
I also did write some tutorials, especially for the HTML/JS Part that access the blockchain, for example: http://www.newscombinator.com/article/8/link-list-on-the-ethereum-blockchain-with-votes
Also, read through the links provided in the "get started" post on /r/ethereum. The community is great, questions are answered quickly.