I added a new feature to xwordinfo.com -- popular words by word length. It turns out TSETSE is the most popular 6-letter word, ALAMODE creams the 7-letter list, and IDONTCARE ties with TALLORDER as the most frequent 9-letter answer. Well, it's fun to see what puzzle creators like. The 15-letter word that pops up most is ELECTRICTOASTER.
The stats keep changing as I go back in time and add more data. I'm back to 2002 now...
Update Dec 13th: I'm back to early 2000 and the stats have shifted. TSETSE still sucks the blood out of all the other 6-letter words but DEADASADOORNAIL kills the competition in 15-letter land. This amuses me for some reason.