The American Mathematical Society provides the latest in mathematicz news. Their site gives links for students, reference sites, and math awareness to keep up-to-date on math news. Maintained by AMS, an organization dedicated to math education and research since 1888.
This ideal research tool is the online component of Weisstein's CRC Concise Encyclopedia of Mathematics providing descriptions of mathematical terms and concepts. Easy to use and provides many visuals and references for further research.