Best get an idea what you want to change or improve in the game. Some questions to ask yourself:
Do I want to change the graphics? If so, where?
Do I want more quests?
Do I want companions to travel with? Do I want them to have individual personalities, or just come along for the ride?
Do I want a greater diversity of monsters?
Do I want a tougher game? An easier one?
Do I want to own a home? If so, where?
Do I want more businesses in any towns?
...and other questions like that. Then check out the Morrowind mod categories on PlanetSpyElderScrolls, and see what's offered. TES Nexus is good, too, but they're more of an Oblivion host--still, they have very extensive discussions of mods that can clue you into what's good, and what isn't.
Then, if you still have questions about what to get, come here and ask in the Mod forum.