I posted this in the Fic Noms thread earlier and July pointed out that they should be nominated to Legendary Goodfic. Considering that I agree, I figured I'd try for at least one more person to get a balanced consensus? Sound good? Here we go.

Brothers In Arms, by the Nightrunners
http://www.fanfiction.net/u/242499/The_Nightrunners
http://www.nightrunners.0catch.com/
Incomplete Modern AU with reincarnation, guns, bands, and everything that I miss about modern AUs. FF.N version has one or two more chapters than the other site but possibly not the vignettes.

Mellon Chronicles, by Cassia and Siobhan
http://www.aragorn-legolas.5u.com/main1.html
Aragorn and Legolas bro-fest so classic it practically created a couple tropes.
Warning: the site still runs perfectly well, but will likely try to tell you that it runs better on other platforms first.

BagEnders, by Lady Alyssa and RandomDent
http://bagenders.stormpages.com/
Modern AU CRACK! This is so much crack that it is Legen-waitforit-DARY. Parts of it are gone, possibly forever, alas. Cult classic, really.