I got this idea from Squizz on The Office boards and will do this for FlashForward. I'll also add a few things like he did once more episodes come out.
09/24/09: 1-01 "No More Good Days" - 12.41 million viewers (4.1 rating in 18-49 demo)
10/01/09: 1-02 "White to Play" - ??? million viewers (??? rating in 18-49 demo)
10/08/09: 1-03 "137 Sekunden" - ??? million viewers (??? rating in 18-49 demo)
10/15/09: 1-04 "Black Swan" - ??? million viewers (??? rating in 18-49 demo)
Season Average So Far: 12.41 million viewers (4.1 rating in 18-49 demo) [Totals: 12.41M & 4.1R]
For those who don't know the most important number is the 18-49 demo. That's the one networks use to evaluate a show being worthwhile to keep because that's what brings the money in on ads. 5.0+ is phenominal nowadays, 4.0 = great, 3.0 = good, 2.0 = average, could be canceled depending on the timeslot. The total viewers isn't as important. So a show pulling 10M viewers with a 2.5 demo isn't as likely to be renewed as a show pulling 8M viewers with a 3.5 demo. It's kind of weird but that's how it works. Also, premieres are typically heavily skewed upward so the second episode will have a larger dropoff. It's not until a few episodes have come and gone that we'll see how the viewers level out and where a show's stability is. I'll update this later today once the numbers for 'White to Play' are released. I'm hoping for 9M viewers at a 3.0+ demo at least.