Skyrim environment enhancing mods

To start off I'll talk about some grass related .ini edits you should tweak even if you're not using mods.
Skyrim.ini
[Grass]

iMinGrassSize=

Are the usual numbers you should use, lower means more grass and lower FPS

iMaxGrassTypesPerTexure=

This one vurts wants you to set to 7, it makes more grass appear. You can use a lower value if you think there is too many grass types rendering.

Skyrimprefs.ini
[Grass]

fGrassStartFadeDistance=
fGrassMaxStartFadeDistance=

These control how far the grass renders, I set mine both to 14000 and I think it caps at 20000.




Flora mesh replacers:

• Bigger Trees - Makes trees much bigger, I think it adds some too. This mod works with mesh replacing mods.
• Unique Grasses - Good mod that adds grass. Can be used with other grass mods.
• Skyrim Reforestation Project - Build your own forests and crash your own game! Likely great for save bloat and adding Immersive™ and Natural™ trees to your cities. Not quite a replacer but I thought I'd mention it since it's a very cool mod.
• Lush Trees & Grass - I highly recommend using the old mesh replacers as the new ones look retarded. I've re-uploaded two sets here and here. It's also worth noting that OpticShooter has actively removed the mods a couple of times and I have no idea why, maybe these old replacers are full of spiders or something. Even so they're the best mesh replacers in my opinion.
• Ultimate Lush Overhaul - I've always just used Lush Trees so my experience with this mod is limited. It's got an FPS hit though.
• Tamriel Reloaded - This is a texture overhaul that probably isn't to your tastes but what it does to grass is amazing.

Flora texture replacers & .esp's for grass:

• Vurts Flora Overhaul - Always trust this guy to fix your flora in video games. Setting this up varies depending on what other mods you use. 
• TreesHD Skyrim Variation - STEP has a guide for getting it to work nicely with VFO.
• Dat Grass - Very good grass mod, most Skyrim 'bullshots' are using this mod.
• Grass on Steroids - Looks bad to me but some like it.
• Glorious Grasses - There are several grass .esp's out there but I really liked this one.

LOD textures:

• AOF Tree LODs - I believe these are the definitive LOD tree textures.

Weather mods:

• Climates of Tamriel - Most use the exterior module.
• Enhanced Lights and FX(ELFX) - Most use the interior module.
• Enhanced Lighting for ENB(ELE) - My personal pick if I had to use a weather mod.
• Tropical Skyrim - Replaces everything and does a decent job at it. Destroys the lore.