Louis Delmas was in fact fined for flipping someone the bird during last Sunday's Vikings game. He wasn't fined by the NFL, though. It was actually the Lions that told him to open his checkbook, because they docked him $5,000 for an "unsportsmanlike act." (Dominic Raiola was fined $7,500 in 2008 for flipping the bird. His fine was likely larger because he did it to Lions fans.)
Delmas said earlier in the week that it wasn't him in the picture, and if it was, it was his pointer finger, not his middle finger. That explanation did not keep him from being fined, but I'm thinking he must have been watching a Shaggy video before he spoke to the media.
Delmas wasn't the only player fined for actions during last Sunday's game. Minnesota's Ray Edwards was fined $5,000 for a roughing the passer penalty and another $5,000 for shoving Rob Sims and starting the scrum that included Shaun Hill and Jared Allen shoving each other. (See Jared, it wasn't the Lions that started it.) Minnesota's Ryan Cook was also fined $5,000. He received the fine for an illegal clip on Julian Peterson.
All of the fines involving Vikings players came from the NFL.