Yahoo Messenger - I only care for video chat from phone to PC, so Yahoo Messenger works awesome for me. I've used it over wifi and 3G while i was on the other side of town and it performed as it should. No lag, good video and audio quality both, and ability to use front or back camera with no problems. I was surprised how well it worked since i was used to Fring or iMovicha4Evo
iMovicha4EVO (in the market) - Fring quality video (poor), same for audio (poor, looping), sometimes unable to connect. But it did have a landscape feature that YM seems to lack. Mixed reviews in the market, but at the time it was the only choice i had to video chat from phone to PC