The design focus on Peer-to-Peer (P2P) networks had been on low-complexity content mapping and efficient search mechanisms, and many of the existing P2P applications provide an efficient substrate for sharing small files like MP3 or images because searching efficiency is essential to the overall performance. For bulk contents like multimedia documents or scientific data sets, however, the data transfer efficiency becomes critical to the overall distribution efficiency. This work explores the use of P2P overlays on distributing bulk contents, and the goal is to improve the distribution efficiency and make P2P overlay a cost-effective alternative to Content Distribution Networks (CDNs). This work addressed two major challenges when designing p2p protocols: neighbor selection and incentive provision. The proposed protocol is light-weight, completely decentralized, and cheat-proof. Experimental results illustrate significant improvements on the distribution efficiency of our protocol over other adopted alternatives.