Panasonic DVD-L50 Portable DVD Player
Can't beat it for now.
I'm sure that in the near future, both Panasonic and others will improve the technology (better and smaller) but for right now, if you want to watch a DVD while sitting on an airport bench, this is the player.  I have had my  player for 3 months and I am very happy with it.  The battery is a little  awkward and 3 hours is barely a movie these days, but I am impressed with  the feature set.  Once ALL the hotels provide TVs with RCA and/or S-Video  inputs this will be the only travel companiion you'll need.