I thought it might be helpful to keep a running tally of some of the best mods around, and what they do, for quick reference. Feel free to add to this, but please, no questions in this thread, and let's keep it on topic. Thanks.
Super Adventurers 3.02.
Adds plenty of tweaks to the game, generally making it somewhat harder (but in a few cases, easier). It's meant to rebalance things more sensibly.
Amulets and Rings.
Adds all sorts to the game, both in shops and as swag.
Adds dialog to many NPCs in these areas. As you know, most NPCs have dialog which is about as interesting as that of economists.
The Cloak Collection.
Adds a ton of cloaks to the game. As I recall, some involve quests.
Cult of the Clouds.
New faction, items, guild hall, dungeon, NPCs, creatures, books, quests. Located on Dagon Fel.
When you get to the top of a guild or faction, this mod gives you the ability some neat new abilities. For example, you can send any member of House Telvanni on a mission as Archmagister, while you can practice combat with any Imperial Legion soldier or guard as Knight of the Imperial Dragon. Really great stuff.
Fair Magicka Regeneration.
Four scripts; you choose one to set the speed at which magicka regens. Note, it affects your opponents as well as you.
The nice thing is that you don't have to guzzle endless potions or sleep to regain magicka.
Guild Guide Quest.
Several guild guides now have their own faction, and you can join it. If you perform all their quests successfully, you gain the ability to teleport instantly to any of those guilds.
Adds new alchemical substances, and removes Fortify Intelligence from the game.
Uriel Septum's favorite resort, the location of a mystery. Not much hack and slash, this is a very good RPG yarn.
. So many mods are located in or near Seyda Neen that crashes and conflicts are common. My preferred mod for that area is this new town to the south, which adds a thieves guild that you help establish. There are 16 thieves' quests, and a nice idea: you get a cut of the guild profits. So the more quests you accomplish, the more you benefit the guild, and the more money you acquire on a regular basis. Also includes a loanshark, betting on fist fights, and an underground bar.
. By the same modder as Haldenshore. This is a major city, on a landmass west of Vvardenfell. Once again, a new thieves guild with 20 quests, but also 8 quests for a fighters' guild, and 8 for a mages' guild. Has a banking system, and gambling--you can play blackjack, and bet on rat fights.
. This is an ease-of-use mod. You put it in your inventory, and it monitors your health. At defaullt settings, if it finds you below 30% of health, it will automatically administer any health potion you carry. This also applies to fatigue. You can change those settings, though, by moving the Bio-Monitor on top of your image in the inventory box. It also has an in-game book with full information about the product. This shows up in Seyda Neen, by the way, on the shop counter, and its a freebie.
. Another ease-of-use mod. Instead of having to open every plant you come accross and extract its contents, this mod makes the process automatic. Click on the plant, and its contents are moved to your inventory. If nothing's in the plant, you'll be told so.