Rotoworld, Razzball, Fangraphs, plus the main sites when they look interesting (Yahoo, ESPN ect). Fantasy Rundown is a nice clearing house type site for sure. I also read Drunk Jays Fans religiously, but not for fantasy reasons.
Im huge Razzball fan --Grey's thinking seems to mirrior mine plus he is hilarious. RotoWorld and MLB Trade Rumors for latest player news. CBS is my home site but info isnt worth the paper its printed on. Hardball Times has some great articles --both fantasy related and baseball history. (Some of their writers are great --others think they are the cats meow. (i know im speaking foriegn language --im old) Roto Summit is new site which I find very intersting and good. Mainwriter is Jesse Sakstrup --he is very accessible. Rotoprofessor is also very good as is Baseball Professor Fantasy Rundown if I dont have much time it points you in direction of sites with latest articles posted. Fangraphs of course
Those are my go to sites --but I read others. RotoAuthority basically just re-launched with new team of writers. (Been almost dormant for couple year) RotoHardball just merged with Fake Teams covers all Fantasy sports Fantasy Windup posts periodic chats with Ron Shandler as season gets closer and during season
There are probably 10 others which I glance at periodically.