Mods I have cobbled together for this:
Utility:
Armor Status (Shows durability, and item count of selected item)
Tree Capitator (Chops down an entire tree, without having to do each block at a time)
Not Enough Items (Shows what recipes are available, and how to make them in the UI)
WAILA - What Am I Looking At! - Shows you some info on the block you are looking at and if it can be harvested, and with what tool
Inventory Tweaks - Organizes your chests, backpacks, and replaces broken tools in your hand
Terrain:
Streams - Adds Streams to the game that have flowing water, and move from section to section. NOTE: I am not 100% on the server load this creates. So I might end up pulling it. I know locally it costs nothing to run.
Biomes O' Plenty - Adds a huge array of Biomes, Tree's, and a Dimension to the game. Its basically variety of where to build.
Big Tree's - Big Tree's
Magic:
Thaumcraft - Adds magic to the game, Golems, and other crap
Enchanting Plus - all this does is cleans up the existing in-game enchanting options
Project E - This mod is broken all to hell, but in a really good way. Anyone that played the original tekkit should remember this mod. It takes a seriously long time to get going, but once it does...... I will let you all explore this one on your own
Witchery - I have no idea.... Seriously, its been a part of FTB and other mod packs for a long time, but I have never explored it.... whats the worst that could happen?
Cosmetic:
Storage Drawers - Storage drawers...... pretty straight forward
Ye Gamol Chattels - Adds a way to display various things
Iron Chest - Adds a variety of Chests, each with larger storage capacity
Chisel - adds in more block styles and shapes
Carpenters Blocks - Adds in more block shapes
Architecture Craft - Adds in more Block shape types
Craft Heraldry - Flags, Banners, and shit
Plants and crops:
Natura - More tree's and plant types
Pams Harvestcraft - more plants and seeds for farms and food
Growthcraft - fruits and other stuff
Dungeons, Dimensions, and Villagers: (Leaving this section vague)
Runic Dungeons
Twilight Forest
Recurrent Complex
Metals, and Ore Processing:
Metallurgy - Adds in loads of ores and alloys, as well as a few different types of furnaces and grinders to process them.