I found a link to the EPIC library on this forum http://www.mindcontrol.org/~hplus/epic/
It actually works well, but only if you're sending it very frequent updates at consistent intervals. My game is like a mini-mmo, so it's Internet based and player packets come at max 200ms intervals. So, the large time delta and the fact that updates don't come through if the player isn't moving really mess this EPIC algorithm up. I think it's made more for a UDP lan game.
Anyway, I can work on writing my own, but I have to imagine someone has pounded out something already. If anyone wants to share or point me to something to help me out, I'd appreciate it.
As a FYI, every player position update packet has: position, velocity, rotation, and time stamp. So, I should have all the necessary info in my packets. Thanks!