The Kevin Johnson 97 SP Authentic Sign of the Times has been super hot in the last several months. It only books at $10/$25, but has been surpassing that range consistently since early last December. The cheapest sale I have tracked was for $17.53 in early February. Otherwise, it has been selling in the $30-$50 range, with one selling for $70+ in late December. There are two currently listed on eBay with a few days remaining on both.
Update, April 23: Well, the first one sold for a measley $14.50. I guess this card has cooled back down.