http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=732
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=1777
http://lovkullen.net/Emma/lokken.htm
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=127 (If you're playing a Mage)
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=4449 (If you're joining House Telvanni)
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=5997 (If you're joining House Telvanni)
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=7040. Map 1 has many quests already (for Telvanni and other factions, along with many miscellaneous ones ) and map 2, though questless, is a lot of fun to explore.
http://www.lgnpc.org/, while focused on dialogue, adds new quests as well. Seriously, if you use the Telvanni based LGNPC mods along with Rise of House Telvanni, Uvirith's Legacy and Tamriel Rebuilt you'll be overwhelmed with Telvanni quests. And that's a good thing in my books.
http://lovkullen.net/Emma/Kateri.htm makes the MW main quest more interesting and he has some quests of his own.
Also if you liked Endrek's Sixth House mod you may want to check out TheMadGod's http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=801 as an alternative. I think it represents the sixth house better than Endrek's mod does, which makes it very evil, whereas the Great House Dagoth mod keeps it in the grey area. But I've played both mods (not at the same time obviously) and they are both great in their own way.