For Ars Technica, I penned this rundown of ways to stay safe on public Wi-Fi: Firesheep takes a techie sniffing tool and makes it mainstream, but there are plenty of other risks as well. Thus, I wrote this guide for Ars Technica on the best ways you can stay safe while using public Wi-Fi.
My main suggestion, as always, is a VPN: whether you rent a VPN connection from WiTopia.net or other such VPN hosts, have a corporate connection, or set up your own. Securing services is second-best, like encrypting email, and using methods to force SSL connections.
Doing nothing is no longer a reasonable option for public hotspot use unless you want a fair degree of certainty that anyone could easily spoof your identity.