Help me choose a small, light PDA-type device for typing text files which I can later retrieve to a computer?

The main purpose is to take it along on hiking trips for journalling. It should have good battery life, and preferably accept a foldable full-size keyboard. Internet capability would be nice but is not essential. I'll look on Ebay for an older model if the price is right, preferably under $100. But if necessary I'll spend up to $300 for a new model. What do you suggest?