Give something from the ASUS eee PC 1xxx line a look. I've been quite happy with my 1005PE. Small, super portable, and a good keyboard.
The 13 hour quoted battery life is more like 11 in my experience, and that was before I put in a SSD. It does vary by model, some googling should get you some real world numbers quick.
http://www.memoryexpress.com/Product...9/Default.aspx