2 problems with shadows, first off, here's my build:

i5-2500k
geforce gtx 570
8gb ddr3 mushkin blackline
asus p8p67 pro (new b3)

My shadows aren't clean like this:

http://www.youtube.com/watch?v=A8LRPKWlvgM

I have everything to "on" or "high" (the highest it can go). The shadows on faces are messy.

Secondly this problem has been going on since I installed the game. The shadows flicker on grass, but only on grass. NPC's as well. Is there any way to fix these problems?

self shadows are borked in oblivion. turn them off.

Thanks, is Bloom or HDR better?

that's just a matter of taste. Try 'em both, see which one you like better. If you want to use the in-game anti-aliasing, gotta use bloom. (but, using the in-game AA also disables screenshots) You can also force AA in your video cards control software. But, depending on what screen resolution you play at, may not even need it.

Something else to check would be the setting in your oblivion.ini (located in My Games\Oblivion, type is "configuration settings")

iShadowMapResolution=?

Values of 512, or 1024 are good, if it is 256..... change it, that causes trouble too.

Thanks again. So, if I was to move up the shadows to 1024, would the self shadows look better on faces and such?

Wouldn't do much of anything for self shadows as it doesn't specifically alter it. Self Shadows is simply just broken. HeyYou just suggested that fix because many lower it from its original value (1024) to get more performance, but it can actually cause problems instead.