Also make sure you follow:
YahooSportsNFL
Michaelombardi
SI_RossTucker
SI_PeterKing
fbg_dodds
joe_bryant
nflcommish
LATimesFarmer
RosenhausSports
BobGlauber
Ed_Thompson
caplannfl
footballpost
profootballtalk
fb_outsiders
JasonLacanfora
Also Im there (SigmundBloom) and of course TheAudible, CecilLammey, Wood83, HermanKickology, fbgchase, JeffTeferTiller, JeffHaseley, JPasquino, Thegutcheck (Waldman), memphisfoundry, maurile - sorry If I'm forgetting any staffers
beat writers off the top of my head:
Dolphins - ArmandoSalguero, OmarKelly, EdgarThompson, MikeBerardino
Jets - TheJetsStream, ManishMehta1
Patriots - MikeReiss, ProjoPatsBlog, PatriotsInsider, RapSheet
Colts - JohnOehser, Coltpower
Texans - ChronicleTexans, TexansInsider
Jaguars - JagNation, Jagsreporter, VitoStellino
Titans - Tnsports
Browns - TheOBR
Ravens - JamisonHensley, RavensInsider
Steelers - JimWexell, scidotcom, stillers
Bengals - ChickLudwig, JoeReedy
Raiders - bydavidwhite, jerrymcd
Chiefs - kb_kstar
Broncos - fs3142, DenverBroncos, Jeff_Legwold, JosinaAnderson
Eagles - Geoffmosher, MovingtheChains, Jeff_McLane, BrianSeltzer
Cowboys - CalvinWatkins, TMacMahon, DCStarJEllis, DerekEagleton
Giants - TheBlueScreen, NJ_Giants
Redskins - RedskinsInsider, PaulTenorio, RickMaese, JReidPost, RedskinsDotCom
Lions - JohnNiyo, TomKowalski36
Bears - BradBiggs, BearReport, ESPNChiBears
Packers - TomPelissero, Greg_A_Bedard, RobDemovsky, MikeVandermause, PeteDougherty, PackerReport, TomSilverstein
Vikings - skjensen, JuddZulgad, chipscoggins, vikingupdate, rickalonzo, vikingsnow
Panthers - DarinGantt, CarolinaHuddle, CharlesChandler
Falcons - DOrlandoAJC
Bucs - PewterReport, HolderStephen, TBBuccaneers
Saints - jeffduncantp, bawtp
49ers - MattMaiocco
Rams - Miklasz, HBalzer721
Seahawks - Dannyoneil, tntsports
Cards - Cardschatter
Most teams have official twitter feed, and there are unofficial news feeds for each team set up that are pretty good. If you just look through who I'm following, you find a lot of those.
I'll add more as I have time and remember them. A lot of beat writers are just now showing up on Twitter. You get a good feel quickly who uses it well and who just uses it to link to their content elsewhere.