The goal of this paper is the development of network coding solutions able to improve the performance of video streaming applications over peer-to-peer overlays. Recent advances in P2P protocols have shown that rateless codes can be profitably applied to P2P video streaming with several advantages in terms of protocol efficiency and simplification, e.g. push based video delivery, no need of packet reconciliation at the decoder. In this paper existing and novel network coding techniques based on rateless codes are presented and compared, showing that rateless codes, besides simplifying the protocol design, can significantly reduce the startup and playback delays. The proposed protocol is evaluated on real topologies, obtained crawling the widespread PPLive video streaming application. The reported experimental results show that the proposed protocol significantly reduces the startup and playback delay and allows one to increase the bitrate devoted to the video stream.