One place to start would be Dapps for Beginners you could follow the progression via Introduction to development on Ethereum and then Setting up your development environment or jump straight to;-
Your first Dapp
The tutorial focuses on your first steps using Alethzero (the development client), and the creation of a simple coin contract – the backend of your Dapp.
The Education area of the Forum
At the same time it would be useful to read / follow / participate in the Education area of the Forum since there are useful questions and answers e.g. Understanding data storage
"Regarding storage fees, you pay both for the size of the Tx in bytes and for the size of the new data put into contract storage. If you remove data from contract storage (I.E. after your tx executes, the total contract storage is smaller), you get a refund up to half the gascost of the tx (you cant get sent ether back, but your tx fee can be subsidized)."
The Yellow Paper
In the Yellow paper Appendix G the fee schedule is specified in units of gas for the fees associated with various computation.
State of the DAPPS
Finally then if you are looking for interesting material State of the Dapps (a Decentralized Application (or 'Dapp') is a piece of software consisting of a user interface (UI) and a decentralized backend; typically making use of a blockchain and smart contracts. Most of the projects listed were built using Ethereum.