Bit of a primer for anyone who hasn’t looked it up recently.
Project Magma
Myth II is now at version 1.5, check for downloads here.
Also available is a full port of The Fallen Lords into MII, check for downloads here.
More addons are available including interface reskins from Chimera and TFL
Flying Flip Studios
Keeper’s of Myth III, its now fully playable with some improvements for multiplayer (you can draw on the map again!) They’ve also updated the map tool Ballistic for function and ease. Try their downloads section here
PlayMyth.net
The Bungie.net replacement, Marius.net is also an option if your interested in a TFL matchup however its an empty place outside the regular thursday (?) night sessions.