These are a few good one's to try out.
*Tamriel Rebuilt is the Best landmass addition. (just google it they have their own website.)
*Darknut's Greater Dwemer ruins makes the main quest dungeons and the sixth house MUCH more interesting. (use it with Julan Ashlander Companion, there's a patch I think that he provides)
*The Horror Mod is a great quest mod, Very little incompatibilities.
*I would use BTB's Game improvements, just make sure to read the readme
, and be selective with plugins to your own taste.
*Dave humfreys furnature mod is neat (also needs a patch)
*Morrowind comes alive and/or Starfires NPC additions are excellent, they add a large variety of random NPC's and companions.
*Children of morrowind is good for the same reason, very high quality.
*Fair magicka regeneration is simple and sweet.
*World of faces is a relatively small face replacement mod that adds a lot of variety (use with Vvardenfell visages.)
*Better Bodies
*Better Clothes
Tools you will probably need...
http://code.google.com/p/mlox/wiki/Mlox Reorders your load order comprehensively
http://wryemusings.com/#WryeMash Managing and updating mods, also use this for merging leveled lists.
http://planetelderscrolls.gamespy.com/View.php?view=utilities.detail&id=34 For Cleaning Plugins and merging objects.
http://yacoby.silgrad.com/MW/Mods/Reordermods.htm: Yep
Also check http://www.liztail.com/
Edit: Oh, and be sure to use the morrowind patch project and the Morrowind code patch. these should get rid of many ussues present in the vanilla game. And depending on you CPU you may wish to use http://timeslip.users.sourceforge.net/exeopt.html Optimizer in order to reduce crashes.