Plasma is old technology, consumes more power, runs hot, colors degrade over time, cheap...
LCD is newer technology, cheaper...
LED is newest technology, gives best color, expensive ;)
I suggest buy 120 Hz LCD, if you dont care about motion blur effects, especially fast paced movies, sports go with 60Hz LCD, you save %50 on price ;)
for example I just bought Sharp Aquos 40" 1080p LCD HDTV** (LC40E67U), for $599.99 ;)