Depends on how the group you are doing the exchange with interprets white elephant... as in, a $20 gift that anyone would be happy with, or a gag gift.
If it's a $20... you could go to walmart (ughh) and look around. They have all sorts of things on sale for just under $20..
That, or if you know your group really well you could get like, a car visor CD holder and a CD that most of them would like. A popular gift last year was a pretzel making kit from Auntie Annies in the mall and small set of gourmet sauces to use with it. A board game is always a good last-minute idea.
The best thing to do is to think of something that they everybody has a need for, or an item that would provide some sort of entertainment.
You'll do better of thinking of a gift if you stop thinking of one item to get, and think of maybe 2-4 smaller items to bundle.