Two on Skype
I've found two good analyses of the Skype voice over IP (VoIP) software: "An Analysis of the Skype Peer-to-Peer Internet Telephony Protocol," by Salman A. Baset and Henning Schulzrinne, and "VoIP and Skype Security," by Simson Garfinkel.
Skype is software that allows you to make phone calls over the Internet. The concept is that by encrypting voice traffic, Skype can keep your calls private from eavesdroppers. EFF is interested in Skype because of its potential for helping people safeguard their privacy on the Internet.
Everyone who uses or is considering using the software should definitely read the Garfinkel article because it discusses in clear, concrete terms what security and privacy trade-offs Skype users make. More technically oriented readers should also check out the Baset and Schulzrinne article, which is similarly clear and substantiates what Garfinkel only speculates about.
While Skype looks like it could be a useful product for Internet voice communication, keep in mind Garfinkel's warning: "[Because] the Skype protocol is both proprietary and secret, the only sources of information are statements from the company about its security and what can be found by reverse-engineering the software." Even though we have some details about Skype, we don't know everything, and we should act accordingly.