As mentioned by the Others, Asus has a a few models which seem to meet your requirements. MSI Has the
U110 which has a claimed 14hr battery life, which is also a decent option.
If the budget has gone up, to get a full lightweight laptop, I'll suggest a Few Options.
Dell has a few good options. For a liitle bit more then the price of a netbook, you can get the
Inspiron 13 which with the extended battery should give you about 5hrs of battery life. If you want to get a more poweful system, the
XPS Studio 13 is a really nice system, which has a good balance of Power and Mobility. They are both 13" laptops, which I personaly find to be a good balance of not beeing too large or small.
Lenovo (IBM) has some superb laptops, especially with the X200 and X300 thinkpads which are very portable sturdy machines. you can find them Very Cheap from the
Lenovo outlet Store or if you want to go for a brand new one, use discount codes form sites like
LogicBuy.