Leyrann
Deity
I would love to see a stickied post with everyone's favorite mods and combination of mods, maybe even with some details as to why they feel it improves the game. I've played around some with mods but have yet to find a combo that improves the flaws of the base game without going a bit too far. I really feel like there is a great game hiding somewhere underneath, just haven't figured out how to bring it out just yet.
You can make a thread in the Creation and Customization forum and ask over there, but in general it seems that the most popular AI mod is AI+, the most popular gameplay mods (off the top of my head) are TCS' Omnibus Mod and Strategic Industry, and the most popular map mods YnAMP and (at a safe second place but my favorite) Larger Worlds and Detailed Worlds. EDIT: And I'd almost forget the MOAR units mods.
(also, I'm gonna look up that AI Siege Help mod... They sure need it)