I personally am not big on all the fancy mods for better bodies, GUI, or any of that stuff. My personal preferences for mods are to include new locations, weaponry, or playable races..All these mods listed will be for Oblivion as I only own the Xbox GOTY Morrowind. Below is a table listing every mod I have tried, my opinion and rating of it after careful analysis, and a link to the link in question, usually from The Elder Scrolls Nexus.
 Playable Races
Opinion: While I have only infrequently used it, I have a Dremora character and I find it to be a very cool extra choice for your race. This race includes two greater powers, one of which gives you a full set of Bound Armor and a Bound Mace like the Dremora NPCs wield. Customising your Dremora is limited to the length of your horns and a slight variation on the dark purple colored skin.
 New Locations
Opinion:As a Warcraft/WoW fan, I enjoy this mod. It add a portal on the road from Bruma to CRT that will teleport you to the Northrend worldspace. At Northrend you can climb to the top of the Frozen Throne to challenge the Lich King himself. Arthas Menethil wields the Lich King's full armor and his runeblade Frostmourne.
Elsweyr-the Deserts of Anequina
Opinion: This mod makes the Khajiit province of Elsweyr accessible and adds many variants of the Khajiit people as playable races while remaining extremely lore friendly. While I have lots to say about it, I will sum it up: LOVE IT!!
Vaults of Cyrodiil
Opinion:This mod adds a vault to every city castle, with unique loot, or other items, and lots of gold. But, be warned that there are guards, and stealing from a vault is by no means easy. Each castle has a "Fake <Cityname> Cuirass" that you can wear to not be arrested in the vault, however stealing the loot in the vault is still a crime. There is also a secret vault key within the castle, usually on the count, however, I will not mention spoilers, such as available loot, cuirass locations, vault key locations, etc. It's more fun that way.
 Weapons and Clothing
Opinion:This mod adds a camp of assassins wearing the white assassins gear of Altair from AC as well as a black variation. The armor can't be looted directly off each individual assassin upon death, however there is a chest located near a tent in site containing all of the armor and weapons from the mod. There is also a custom race that adds Altair's likeness as a custom race that REQUIRES a custom race mod.
Opinion:These lightsabers are real lightsabers with the glow and everything. They are quite strong and I enjoy using them. They are scattered in the IC Market District. I will leave their locations undisclosed for suspense.
 Companion Mods
Opinion: This mod adds an Argonian Battlemage as a companion with all that being a companion entails, such as sharing equipment and providing combat support and what-not. Ruin is struggling to escape his dark past and will occasionally start a philosophical/morality conversation with you. How you answer affects his outlook on life. The whole mod also includes a quest, where you have to help Ruin escape his dark past and a Sect he used to be acquainted with. I love this mod because it fully develops who Ruin is and why he has this internal strife, and it creates a character that the player can relate to. This mod, to me, is so great that I can not give it justice with words. I recommend it to whoever reads this. Kudos to the maker!
 Snowmane's Must-Have Roleplaying Mods
Real Sleep Opinion: This mod adds the necessity to sleep regularly to the game, with negligence resulting in a decrease of your attributes. I like this mod because it makes the game more realistic. After all, who can stay awake for 3 years straight, resting for an hour a week to level up?
Alternate Start By Boat
Opinion:This mod starts the game by filling immigration forms rather than escaping prison. It does not interfere with the main quest and after the forms are filled you receive free stuff based on the answers on the forms. I like to use this mod so that I am not pulled into the Main Quest right away.
Hunger and Thirst Survival Opinion: This mod makes eating and drinking a NECESSITY! If you don't have a meal every so often you enter stage 1 hunger/thirst. There are 5 stages of hunger, and neglecting to eat will result in death shortly after reaching stage 5.
 Other Mods
Opinion:I only use the realistic physics for magic, and enchanted weapon attacks simply because I found it annoying the fling bodies around instead of them dropping dead. I have not tried out ragdoll physics or the 'low' or 'high' variants of magic and enchanted items opting to keep them as medium.
Lynge's Unlimited Death Reload Time
Opinion:This mod's sole purpose is to delay the menu puling up upon your character's death. You can press escape at anytime to enter the menu. The mod really has no purpose unless you care to throw yourself off of Dive Rock and watch your corpse tumble down, which I do really enjoy doing for some reason.
Obscuro's Oblivion Overhaul
Opinion: This mod does such a large number of things that I could not begin to list all of them, so suffice it to say its a great mod and a must-have.
 Discontinued Mods
These are mods that I have thrown out for whatever my reasoning at the time was. These are not necessarily bad mods, I just don't have a use for them at the current time.
Playable Golden Saint
Opinion: This mod makes Dark Seducers and Golden Saints playable. This mod, obviously, REQUIRES Shivering Isles to play. When I use it, after I select my Golden Saint, I get put into the void, unable to go to my Alt. Start Immigration fomrs to create class. I don't know if it is a conflict with the mod or just a messed up mod, but I am not able to use it and won't. If it is my Alt. Start mod, I will just do without the GS mod, because I lke by Alt Start mod.
Opinion:This stronghold, to the west of Anvil is fairly unimpressive to me as it is simply a version of Cloud Ruler Temple. It has its own uniquely named Blades guards, however They are simply copy and paste the Cloud Temple guard with different names. The key to open the front entrance can be located in the Cloud Temple Armory.
Capes and Cloaks
Opinion:This mod adds capes and cloaks to Divine Elegance in the Market District. The cloaks and capes are head gear items forming a hood with a cape going down the back. Perfect for the aspiring Jedi when used in conjunction with the Lightsabers mod. I personally use the black Cloak with the black variant of the AC armor and a lightsaber. I discontinued this mod simply because I never have time for using it.
Opinion:This mod is actually EXTREMELY impressive. It adds a fantastic castle stronghold to the game and a couple quests to make it your own. It easily overshadows Battlehorn, Forstcrag, etc. To begin the quest, you must speak with a new NPC in the Inn of Ill Omen. Note that the activators for the things, such as moveable pillars that open secret passages, have had the activator hand removed, so you need to be creative and experiment with the environment if you suspect a hidden activator in the area. I discontinued this mod because after literally hours of searching, the lack of switches and vague directions became too much effort to be worth my time.
The Lands of Solstheim, Vvardenfell, and Mournhold
Opinion:This mod add the lands above, from TES3, to the game, accessible by boat from Anvil. It also adds the MW versions of birthsigns, races, and classes. It is only Beta V.1, so I won't use it until the next update, estimated to be released before Skyrim.
 Ideas For Mods
These are ideas for mods I have that I would hopefully like to begin after the first of the year.
Become Emperor by Conquest
Upon completion of the Main Quest, It would be cool if you could become the emperor by conquest. Using your powers as Champion of Cyrodiil, you could rally the spirits of fellow legionnaires and city guards, etc. and then assasult the capital with the intent of killing Ocato and grabbing the Emperor's Crown. Upon victory everyone could address you as "Emperor," "Your Majesty," etc. and all the Palace becomes public ground for the PC to travel in.
A Complete Tamriel
Just as Elsweyr-the Deserts of Anequina adds Elsweyr to the game, it would be cool to add the other provinces to the game in an Area-ish style of everywhere being visitable, but with the quality and detail of Oblivion. However such an endeavor would take a long time, upwards of years to accomplish, and several people with a knowledge of lore and the Construction Set to create.
Martigen's Monster Mod-- Looks cool, but I haven't used it yet. I'll have that one tested in the next few days.