Are you sure you are looking for a rear projection LCD and not a flat panel LCD set? The flat panel sets are as thin as plasmas and lighter in weight than plasmas. They are even brighter than plasmas and are therefore well suited to a room that does not have good light control for tv viewing. The flat panel LCDs are better than rear projection LCDs with respect to brightness and have richer, better saturated colors.
I believe that LG has a 50" flat panel LCD and Sharp has a 47" model.
The downside to all LCD sets is that they are a bit slow in response to rapid changes in the image. Also, black levels are not particularly deep on any LCD, making dark scenes in movies a bit murky. The other big downside for the flat panel LCD versus the rear projection LCD is the higher price of the former.
Another thin option to consider is the rear projection DLP sets from In-Focus and RCA. They have 50-60" sets that are only 7" deep. I saw them at CEDIA and they looked surprisingly good. I expected to see focus problems and geometric distortion at the edges, but nothing really gross showed. Like all DLPs, these sets do exhibit "rainbows" to those prone to seeing them (that includeds myself, although I can ignore them). The big negative is that these sets are priced like big plasmas.