Well people here's our list of known, tested and worthy Skyrim tweaks.
Also a bunch of mod that we recommend.
Be sure to check back often as we'll keep the list updated.

Basic Tweaks

- Avoid setting the shadows on Ultra. Keep them on High as the difference is minimal but Ultra really hits the framerate and the blockiness stays more or less the same.
- Uncheck in the launcher graphics advanced options the "Object Detail Fade" under the View Diostance tab. By doing so the game will render at better detail objects like castles far away.
- Those brave enough and with 4Gb of RAM can download the Large Adress Aware program and patch your tesv.exe too support more than 2Gb of RAM. Back-up your file first of course.
- Use FXAA if you preffer a slightly blurry image but without any jaggies as


Advanced tweaks

All tweaks go into [My Documents][My Games][Skyrim]SkyrimPrefs.ini

- Enabling "Data Files" in the launcher - for mods
add this to the [Launcher] section
bEnableFileSelection=1

- Enable anti aliasing for transparent textures (includes some foliage, water, etc). Disable if you get transparent faces or other glitches.
bTransparencyMultisampling=1
iWaterMultiSamples=1

- Enable shadows on trees and all terrain!
bTreesReceiveShadows=1
bDrawLandShadows=1
bDrawShadows=1
    
- Try to reduce mose lag
bMouseAcceleration=0
fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0

- Boost overall audio volume
fAudioMasterVolume=2.0000

- Remove various on-screen markers and compass for immersiveness.