Heh, I have a usual stock response recommending mods to people who ask, but it seems very odd to be doing so to someone as regular around these parts as you!
Some of these change gameplay, so I'm not sure how closely this meets your brief, but here goes anyway:
Unofficial Patch, Unofficial Dawnguard Patch, Unofficial Dragonborn Patch, Unofficial Hearthfire Patch, Unofficial High Resolution Texture Patch.
Alternate Start: Live Another Life - http://skyrim.nexusmods.com/downloads/file.php?id=9557 - Allows the player to skip the helgen intro/start sequence. Very useful for roleplaying. Also allows you to return to helgen and pick up the main quest if you want to later on.
More Interactive Items - http://skyrim.nexusmods.com/downloads/file.php?id=3562 - Immersion mod. Allows the player to pick up and interact with the various bits of clutter (rags, bones, urns etc.) that can be found in the game.
Frostfall - http://skyrim.nexusmods.com/downloads/file.php?id=11163 - Essential in all my games. Completely customisable, as lite or hardcoe as you like.
Piratelord Loot Adjustments - http://skyrim.nexusmods.com/mods/17930/? - makes all barrels and urns activatable, and rebalances loot found within - adds a load more clutter items (broken ancient amulets, steel rings etc.) with a small chance of decent loot. Makes more sense - for example draugr won't have gold in form of septims but as Ancient Nord Coins which are tradable for cash, and dwemer containers have dwemer coins.
Dynamic Things - http://skyrim.nexusmods.com/downloads/file.php?id=32448 - Chop down trees to make wood (compatible with Frostfall), pick up wood from the various vanilla firewood stockpiles (beware, some may be owned!), makes all keg barrels activatable, gain experience when using training dummies, etc. Compatible with Piratelord's Loot Adjustments.
A Quality World Map - http://skyrim.nexusmods.com/downloads/file.php?id=4929 - As mentioned above.
Interesting NPCs - http://skyrim.nexusmods.com/downloads/file.php?id=8429 - A work-in-progress - grab the Voiced Only Version if you want voiced dialogue. Adds new NPCs which are very interesting and amusing - some are "superfollowers" who have dialogue relating to vanilla locations and quests - far more developed than Serana. Many new quests added.
Inconsequential NPCs - http://skyrim.nexusmods.com/downloads/file.php?id=36334 - a very new mod, but already a must-have. Inspired by Interesting NPCs, it adds NPCs such as inn patrons, shoppers, street urchins, students at the college, prosttutes etc. to appropriate locations. All voiced.
Even Better Quest Objectives - http://skyrim.nexusmods.com/mods/32695/ - updates quest descriptions for better roleplaying and so you don't have to rely on quest markers.
Better Dynamic Snow - http://skyrim.nexusmods.com/downloads/file.php?id=10383 - makes the dynamic snow shader look much nicer, no noticable performance impact.
Bring Out Your Dead - http://skyrim.nexusmods.com/downloads/file.php?id=14178 - expands the vanilla graves system to account for the vanilla NPCs without graves. If an NPC dies, their possessions can be found buried alongside them.
Fires Hurt - http://skyrim.nexusmods.com/mods/28202/? - no longer can you stand in a fireplace and not take damage. Adds fire damage to fires and hot geysers.
Footprints - http://skyrim.nexusmods.com/downloads/file.php?id=22745 - adds footprints to player and NPCs. Makes such a noticable visual change I cringe when I see videos without it. Also helps for tracking.
Guard Dialogue Overhaul - http://skyrim.nexusmods.com/downloads/file.php?id=23390 - unlocks plenty of vanilla dialogue provided by Bethesda in the game files but which they decided not to incorporate. Not technically a bug, so not fixed by the Unofficial Patch - but highly recommended to make the guards more interesting (and be more respectful to you when you deserve it!)
Run For Your Lives - http://skyrim.nexusmods.com/downloads/file.php?id=23906 - prevents peasants and shopkeepers from trying to take on a dragon and dying immediately, leaving the gameworld empty and potentially breaking quests. All non-warrior NPCs will now run for cover when a dragon attacks.
Ely's Community Uncapper - http://skyrim.nexusmods.com/downloads/file.php?id=1175 - Bah to the official Legendary mode. THIS is the way to allow higher levelling.
SkyUI - http://skyrim.nexusmods.com/mods/3863 - as mentioned above. Pretty essential for many players - adds Mod Configuration Menu ("MCM") to allow other mods to have custom menus and settings that you can tweak.
Skyrim Immersive Creatures - http://skyrim.nexusmods.com/mods/31256 - adds new enemies to leveled lists. Comes with a "purist lore-friendly" MCM menu if you find some of the creatures out-of-place, and you can toggle various creatures and spawns on and off according to your own tastes. v6 is light years improved from previous versions - v6.1 is now available.
Immersive Armors -http://skyrim.nexusmods.com/mods/19733
I also hear there's a good expansion mod called Falskaar... 
Some of these mods require SKSE script extender - you can grab that from here: http://skse.silverlock.org/
You also need BOSS to sort your mods into the correct order to prevent issues that can arise with mod conflicts - grab the installer version from http://code.google.com/p/better-oblivion-sorting-software/downloads/list
Also you will eventually need Wrye Bash to merge leveled lists together and prevent additional conflicts - grab that from http://skyrim.nexusmods.com/mods/1840/?
Clean your master files and mods with TES5Edit - http://skyrim.nexusmods.com/mods/25859/?
I purposely haven't added graphics mods that are just pure mesh/texture replacers.
Ok, as for your specific questions:
3) Gopher's "perk" mod is SkyRE - http://skyrim.nexusmods.com/mods/9286
6) More spells - I use Lore-Friendly Spells - http://skyrim.nexusmods.com/mods/34620
Skyrim Immersive Creatures (as linked above) also includes a few new spells.