This book constitutes the refereed proceedings of the second International Workshop on Mobile Entity Localization and Tracking in GPS-less Environnments, MELT, held in Orlando, Florida, USA, in September 2009 in conjunction with the 11th International Conference on Ubiquitous Computing (Ubicomp 2009). MELT is a forum for the state-of-the-art technologies in mobile localization and tracking and novel applications of location-based services. The research contributions in these proceedings cover significant aspects of localization and tracking of mobile devices that include techniques suitable for smart phones and mobile sensor networks in both outdoor and indoor environments using diverse sensors and radio signals. Novel theoretical methods, algorithmic design and analysis, application development, and experimental studies are presented in 14 papers that were reviewed carefully by the program committee. In addition, three invited papers, with topics on location determination using RF systems, Cramer-Rao-Bound analysis for indoor localization and approaches targeting mobile sensor networks, are also included in the proceedings.