Mintek MDP-1770 7-Inch Portable DVD Player
loaded (including A/V input) and works fine (so far)
If you buy this, buy the Mintek 1770 Kit, also sold here at Amazon.  With the new rebate, you get the kit for the same price, but in addition to the player, you also get the case, car power adapter, headphones and audio splitter.  My kids have been using this player for 2 months, including one very long road trip, and so far no problems.  I am a bit nervous given the number of very negative reviews here at Amazon (most of which were done after I bought mine), and the fact that the manufacturer is a small company (that's the only reason I didn't give it 5 stars).  However, now that there is a $50 rebate bringing the price down to $200 (not available when I bought mine), and the set includes a decent case, car power adapter, and 2 headphones with an audio signal splitter, not to mention the tremendous functionality, it's such a good deal that it may just be worth taking a chance on.  Amazon is always so great about quickly replacing or refunding defective products within 30 days, that at least takes away some of the worry.  As for battery life, I let Return Of The King run on it and the battery died at just over 2 1/2 hours (not great, but Amazon sells extra batteries for this unit, and for the price, it's hard to complain).  One great feature that the product description doesn't include is the A/V input.  You can play video games on this, or view your digital photos straight from the camera, etc, since you can plug an audio and video source in.  Depending on the type of game console you have, you may need to get an adapter to convert the RCA output from your game unit to 1/8 inch miniplug format to plug into the DVD player, but these are easily bought on Amazon or other electronics stores (ie, Radio Shack) for less than $10.  If your game unit or other outside video source has RCA jacks, then you're all set because this DVD player comes with a cable that has RCA plugs at one end and miniplugs at the other.  But if you have a GameCube (no RCA jacks, just RCA cables),or a digital camera with a USB-RCA cable, then you'll need to get the RCA-miniplug adapter (again, it's cheap).  Here's how you can input video to the screen on this DVD player.  There is a switch on the side of this DVD player that toggles the A/V jacks from output to input, thereby telling the screen to display the DVD or an outside video source.  Just make sure you switch the A/V back to output before you try to watch a DVD again.  If the switch is on input and you try to watch a DVD, all you get is a black screen.  I thought mine was broken until I toggled the switch back to output, then the DVD displayed fine.  I wonder if any of the other people who said their screen stopped working accidentally toggled this switch to input?  Anyway, I won't buy a second one until this first one proves its durability a bit longer, but at two months old, it's working fine and is definitely the most loaded player around for under $500 (and Amazon is giving it away for $200!).