I currently have an unrooted Evo using PDAnet/easytether to tether my phone to my PC. I am wondering if it is possible to tether to a server to provide internet to my network. If it is possible, are there any configurations I need to know? Also, how might this effect the speed?
If you're using Android 2.2's native tethering, then the phone acts as an access point. This means any Wifi-enabled devices can tether to the phone as if it is a regular wireless access point.
I don't know much about PDANet/Easytether, but it should be possible to set up "Internet Connection Sharing (ICS)" on Windows or "Masquerading" on Linux.
Speed will probably be not that great, since 3G is pretty slow on most areas. It will be usable, but unless the 3G speed in your area is blazingly fast, don't expect much.