In the current absence of the Perseus program, and the Perseus dictionary version of Lewis & Short being available sporadically only, here is a scaled down version of Lewis & Short Latin Dictionary, via David Meadows' rogueclassicism and Stephen Carlson (see below):
Archimedes Project Dictionary Access, containing a number of dictionaries of interest to people interested in the classics.
More on the Archimedes Project can be found in this blog by Stephen C. Carlson. According to this, as of April 20, Perseus is back up. However, I'm still having problems . . .