Sony probably makes the smallest, they are like Nintendo DS size, 8" screen or so. There are a ton of 9" screens all the way to 12" in the"netbook" category.
All with Intel Atom processors that can barely run Windows XP. Now Acer has the Timeline series which I'm considering, they are going to announce andlaunch the 11.6" version soon (13, 14 and 15 inch are already available). It will have a slightly better processor than the other netbooks but they willstill be painfully slow for anything other than websurfing and basic word processing.
Dell, Asus, Acer, Sony, MSI, all make tiny underpowered netbooks.