vr :
this one seems pretty good despite the weird elevator music in the background, a nice large text box for long texts and a choice of girl voice or boy voice (or second girl voice in english, which is hilarious if you make her read french text). you'll need to have java installed. there's also
this one with waaaay more voices (and languages !!) to choose from but the pronunciation is a little more robotic, not as good as the first one. for an individual word it's probably fine. oh, and it has animated heads to say your text, which follow your mouse around. a little creepy !