The Linksys RVS4000 and WRVS4400N can block various IM and Peer-to-Peer applications by name (i.e. Yahoo, MSN, etc) and like most non-pro firewalls, can block specific ports. As others in the thread mentioned, you can also use a software-based firewall on your PC to provide even more flexibility in blocking PC host applications. I use McAfee Security Center since it is an all-in-one (Firewall, Spam, Anti-Virus, etc) and I get the home license free through my office. No brainer.