I'd personally reccomend The Tomato Head...the kepner melt is amazing. and their vegan cupcakes are sooo good ^^
Tomo on Kingston Pike, while not exclusively veg, has really good veggie sushi and other vegetarian entrees. The Mellow Mushroom (2 locations: the Strip or Campbell Station) is a sweet pizza place that has many vegetarian options. Charlie Pepper's on the strip has some good options as well. Pelancho's Mexican Grille has a good veggie chimichanga and other veggie options (although I live in a suburb of Knoxville and personally prefer our Mexican restaurant, El Cantaritos :P ) Organic Roots Cafe on Kingston Pike is supposed to be good, even though I've never been. I'm looking at their menu right now and they seem to be 100% vegetarian and can serve raw.