I think one of the better sites for that was divx-compare.com
It's in French though, but if you can figure out your way, you can make searches and narrow down your searches by features. It used to have an English section, but not anymore.
Other than that, if you go to manufacturers' sites, they'll often have the manual in pdf format, and you can look it up to find out exactly what is supported.
A little help if French isn't your forte:
go here http://www.divx-compare.com/section-1-lecteurs-divx.htm
then click on "Afficher plus de fonctionnalités..." which means "display more features".
I think the box you wanted to check is "USB Host (in)". Check it, then click on "Filtrer suivant mes choix" which means "filter according to my selections/choices".
If I can help you with any other translations, ask away.