I upgraded my router to a Cisco rv042 specifically for VPN. Works great with pptp VPN on the TP. Now if I could just get pptp VPN on my Pre3, I'd be happy camper.
I don't think trojans and other direct incursions are what the OP is concerned about. The biggest risk of using public wifi is session hijacking and packet capturing. Using a vpn encrypts all of the traffic going over the wifi back to your home network where it is safe(r). For some applications, like splashtop, VPN could be very useful, as splashtop is sending the data in the clear, so any packet sniffer could eavesdrop or potentially hijack the session.
Best advice for public wifi is to be smart about what you do while you're on it, and to use https connections as much as possible. Most current SSL/TLS implementations are kind of weak, but they're a lot better than nothing.
I'm looking into VPN as well. If I find a good solution, I'll post it.
-- Sent from my HP TouchPad using Communities