Centralized networks and their clients
This list is not exhaustive.
- DirectConnect - (Windows) - a semi-centralized alternative. P2P file sharing and chat. Does use client/server model, but server is free.
- eDonkey2000 - (Windows/Linux) - Client-server based sharing/chat network with sophisticated multi-source downloading (download from someone else even when they're still downloading the same file). Server is free, therefore there's a pretty large server network.
- Filetopia - File sharing with public key encryption. Has Napster-style file sharing, chat & private sharing channels, instant messaging, e-mail gateway, list management, and more. All connections are encrypted, and the author provides a Java program that can act as a connection anonymizer. Server is in Spain. Very promising.
- KaZaA - (Windows/IE4) - A semi-centralized general file sharing tool using a self-organizing network that automatically assigns more tasks to peers with higher bandwidth. The development is closed-source, and a subscription model is being planned. The software is licensed to third parties like MusicCity ("Morpheus") and Grokster. While the original KaZaA contains nasty SPYWARE, the licensed versions usually do not.
This list has only networks that are in use or under development. Please also see The Halls Of The Dead for clients and projects, which have gone quiet.