Merriam-Webster Online keeps track of how often certain words are looked up in its online dictionary - and then names the one with the most lookups the "Word of the Year. In 2008 it was, perhaps not surprisingly, "bailout."

The top 10, in order. They seem to reflect the times and the politics.

bailout
vet (I'm betting this was as a verb, as in "Who vetted Sara Palin?)
socialism
maverick
bipartisan
trepidation (related to Bush?)
precipice (ditto)
rogue (ditto)
misogyny (related to how people were feeling by the end of the campaign season)
turmoil (as in "financial")