I don’t have any actual experience with this class of computers. However, Googling it revealed the following:
For cheap machines, check out “touchscreen netbooks”. It looks like ASUS makes some around $550 and HP (Touchsmarts) around $750. Dell has the Latitude 2110, and the XT2, which is a more expensive version.
This concept Toshiba machine looks interesting. It’s a small dual 7" touchscreen “ultramobile” that runs Windows 7. You could do some cool things with the two screens.