There will be a nationwide protest by some of the world's largest Websites on January 18, 2012, in opposition to the Stop Online Piracy Act (SOPA), which is currently making its way through the House of Representatives, and the PROTECTIP Act (PIPA) which is currently making its way through the US Senate.  Large sites such as Wikipedia, OpenDNS, Mozilla, WordPress and many others will be off-line in protest.  If you are trying to get to your favorite site tomorrow, but you discover that it is unreachable, there is a good chance that they are down intentionally in protest of these two proposed laws.

Here are a couple of links regarding this protest:

http://www.zdnet.com/blog/btl/google-to-protest-sopa-alongside-wikipedia-reddit-others/67219

http://www.popsci.com/technology/article/2012-01/wikipedia-joins-legion-sites-going-dark-wednesday-protest-online-piracy-legislation