XBSlink is described as 'Alternative system for online gameplay on PS2/3 and XBox 360'. There are three alternatives to XBSlink for a variety of platforms, including DeSmuME, Dolphin Emulator, Linux, Mac and Online / Web-based. The best alternative is PlayStation Network, which is free. Other great apps like XBSlink are XLink Kai (Free) and Wiimmfi (Free).
PlayStation Network, often abbreviated as PSN, is an online multiplayer gaming and digital media delivery service provided/run by Sony Computer Entertainment for use with the PlayStation 3 and PlayStation Portable video game consoles.
XLink Kai is a global gaming network - bringing together XBox 360, XBox, Playstation 3, Playstation 2, Gamecube and PSP users, in one integrated community. It is software running on your PC or Macintosh that allows you to play system-link enabled games online for free.
The Wiimmfi service is an online gaming service that provides free online play in various Nintendo DS and Wii games. It has replicated much of Nintendo WFC functionality and allows to continue online play in Mario Kart Wii and other games.