Secure communications are key to global guerrilla ops. One way to accomplish this is through the use of wireless network hacking and Skype. A simple process (amplifications are welcome):
1) Sniff for an unguarded WiFi access point using a tool such as Netstumbler ($150). Focus your efforts by using a map of known networks.
2) Connect to the network using a WiFi enabled PDA or laptop. IP address will be delivered from the network (not likely to be on the FBI's Dragonware list). A low cost directional antenna can extend range markedly (a wok, Chinese parabolic cookware, or the venerable Pringles can -- using Chinese cookware is new but effective).
3) Launch Skype using an ad-hoc profile (change frequently). Skype will provide P2P voice and chat communications with strong encryption.