Rexa
Developed by the Information Extraction and Synthesis Laboratory at the University of Massachusetts Department of Computer Science, Rexa is search engine and "digital library" covering the computer science literature as well as the researchers who create it. The goal of Rexa is to facilitate the "research progress and collaboration by providing efficient browsing, search, associations, and analysis among papers, people, organizations, venues, and research communities." Rexa is free, but registration is required. More information can be found at http://rexa.info/about.