What is the best (and cheapest) pda if I want to be able to search the internet and instant message people?

T-Mobile has a Sidekick for text messaging, but I don't think it surfs.

You can get several models that have built in WiFi that allow you to surf and IM as long as you are within range of a hot spot. But you may have to pay for the hotspot.

Probablky your best bet is a Blackberry or Smartphone, but they will be pricey.