Linguistically, it seems to have a Germanic/Saxon origin, so it would probably be pronounced TOO-luh (as CdCf says). The "e" is a schwa, so it's pronounced very softly (like the "a" in sofa). TOO-lee is a regionalization and probably how most people pronounce it, but that "Th" is definitely pronounced just plain old "T".
/dork mode. Sorry about that...