Asus EeePC 900 only $339 at OnlineComputer for OCAU special
The EeePC 900 (not to be confused with the 900HA or 901, these are different computers) weighs only 0.99kg.
The EeePC 900 is an 8.9" netbook based on the Intel celeron m CPU. This differs from the $475-$600 dollar netbooks in that the newer ones run the intel Atom CPU - a better/newer CPU.
Further, this model does not have the long life 6 cell battery, only the original 3 cell battery.
Like other netbooks it comes with XP Home.
It also has wireless b/g built in but not Wireless N. For only $339, though, it's a steal.