My husband and I have all our mail sent to his parent's address, then once a week they send it all to us wherever we are in one big envelope.
We just get high speed internet & cable hooked up each place we go. If you go with cable, you don't have to sign any contracts,and you don't have to buy any equipment, just return the cable box & modem when you move. It works out well, too, because a lot of cable companies will offer deals, like a lower price or more channels (free HBO, etc...) for the first 3 months- when you move every few months, you can take advantage of those specials a few times a year!
Don't know about the PDA, don't have one....