AReyeP's and MCS' Wolfenstein 3D Addons is a Wolfenstein 3D page created and maintaned by AReyeP and MCS (you don't say). Rather rich in content, other than the expected downloads (as well as manuals, hintbooks etc) for Spear Resurrection, End of Destiny, WolfenDOOM or Wolfenstein Collection, you can find stuff like utility downloads, numerous coding tutorials or AReyeP's older Wolfenstein mods.
AReyeP and MCS' Wolf 3D Add-ons is also a collective title for the series of mods following on from Spear of Destiny by (take a guess) AReyeP and MCS. The new features and ideas contained within these releases were revolutionary for the broader modding community.
AReyeP's stand-alone WolfenDOOM (2000) and MCS' Wolfenstein Collection (2000) is also hosted there, as well as downloads for AReyeP's even earlier First Add-on and Wolf Odyssey. Resurrection was also used as a base for Richter Belmont's The Rise of Hitler.