FooBar is a classic name in program examples, documentation etc (AmericanCulturalAssumption?). Some have been of the opinion that it's a cleaned up version of its cousin FuBar, but this seems unlikely; its etymology appears to be quite different. The canonical sources of information about this are the JargonFile at http://www.catb.org/~esr/jargon/html/F/foo.html and RFC 3092 (at numerous locations, one of which is http://www.faqs.org/rfcs/rfc3092.html.)
I enjoyed reading that it might have originated (in one of its streams of origin) in the German furchtbar (furcht means fright or terror and bar is the adjective suffix for -able, so furchtbar means 'terrible'). Then it certainly makes sense that in WWII the English speakers, who borrowed German language into their slang, would shift it to the slang and acronym form FUBAR (F---'ed Up Beyond All Recognition) to describe something in their situation. . . . The other streams of origin, backing into the comics of the 1920s and the Chinese fortune-cookie word Fu for happiness, are equally interesting.
In CS/hacker circles, foobar (and others) are known as MetasyntacticVariables.
At work, we had a mascot named FooBar. It was an insect (don't know which actually). -- AurelianoCalvo.
See: FuBar (after bracing one's self)