With instant messaging (IM) rapidly gaining popularity among internet users, it's use for business purposes is becoming a practical reality. However, with five major protocols vying for the public's attention, choosing one instant messaging application for your business without limiting the amount of customers you are able to communicate with is nearly impossible. Furthermore, having multiple clients for different protocols hogs resources on your workstations, and can cause training headaches for your employees.
Rob Valliere has released an excellent analysis of Linux as a Windows 2000 replacement. The article has a nice list of Linux-equivelents to Windows applications, and a cost analysis.