Newhaven have just announced a couple of new 7" capacitive touch panel that should work well with the A20 or any of the other Olinuxino boards.
This is cheaper than the one I am currently using. I have used their 5" TFT panels for a Gadgeteer project in the past and they are very nice. The touch driver is fully supported by Android (and most likely Linux) as it's the FT5x06.
I may have to consider these as an alternative to the Touch Revolution one I am currently using. :)