Below is a list of White Paper PDF links for some of the more popular projects out there, old and new. This is obviously not a complete list as there are hundreds of projects out there and much more on the way. This should, however serve as a resource for anyone looking to dig into some of the projects in the space.
Augur-A-Decentralized-Open-Source-Platform-for-Prediction-Markets
CryptoNote (Dash, Monero, Bytecoin)