If you haven't played Glest, you may as well consider yourself out of touch with the world. I recall following Glest before it reached version 0.7 and thinking it was amazing. Over a period of a few short years, Glest has exploded into a full-fledged RTS that deserves to be put on shelves.
Glest is your classic Technology vs. Magic real-time strategy. Reminiscent of Warcraft III, you use your mouse to issue commands to your troops. Build structures, train units, and amass an army to wipe out the enemy.
Glest features full multiplayer support over LAN or IP, so you can get a few friends together and play head to head.
While Glest is great on its own it also hosts a feature that very few freeware games have - mod support. Nearly everything in the game can be changed through the simple editing of XML files. Change the models, the spells, the textures, the levels, and anything else you can think of.
The only thing I wish you could have direct control over is the AI difficulty. Even on the lowest setting, I have trouble beating it. Either it's too hard or I just suck. Either way, it's not a terrible problem.
Glest is one of the few free 3D RTS games and it's good, too! So quit reading this review and start playing it!