I think you have to set up a firmer set of paramaters, you have an idea of what you are looking for in battery life, but what about weight? Cost? You also mentioned performance, but if this is just going to be internet and typing notes a Celeron will work just fine and save the expense (and some juice) over a more expensive processor.
Give the Thinkpad X60 a serious look, with the 8 cell battery it should give you the life you are looking for and seems to fit the bill in other areas.
