Each person puts the code on their home page, and members are added easily. You just need one person to maintain it, and the benefits can be tremendous. Get your network to be as professional and responsible as you would be in the real world. One bad piece of your network can bring everyone down. Make sure that you ask the right questions and take the time to find good partners, not just links.
Sponsorships are a great way to work closely with other sites.
At the Forbes Web Site, Fidelity sponsors a specific section. Their articles and advertising are the only ones you will find in this section. Use these sponsorships to your advantage. Place content at other's sites, and use sponsorships as an ultimate form of networking. Work your way up to this via experience and the ability to mutually generate leads for each other.