If you plan on looking up a term on Wikipedia tomorrow, it looks like you will be out of luck (unless you read a foreign language). The English-language Wikipedia site is planning a blackout in protest of anti-piracy legislation currently under consideration in Congress. See Wikipedia's official statement and a related article in the Washington Post. See also information from THOMAS about the proposed legislation at issue: the Stop Online Piracy Act (H.R. 3261) and the PROTECT IP Act (S. 968).
Legal information and research resources from The Ohio State University's Michael E. Moritz Law Library