Jeromme Le Banner trained in JKD for years before going professional and he has been very successful in his fight career. He is the only 'fighter' that I know of that openly claims to have practised JKD. He mainly fights K1 and other kickboxing events so I know it doesn't answer your question about MMA fighters.
I haven't heard of anyone in Pride, UFC, KotC, etc that openly claims to practice JKD.....
http://www.fightingmaster.com/fighte...ner/jerome.htm