Re the "oh noes, we must replace so many players!!!!111!" thing I saw a ways back in this thread: no we don't.
VDS: De Gea
PIG: Hasn't left yet, but if he does, Lindegaard
Neville: I will say nothing bad about Gary Neville. I will simply note that replacing his production last year is...not hard. Really, the twins not both getting injured so bloody much'd more than take care of that.
Brown: Jones
O'Shea: TBD
Gibson: Cleverley
Hargreaves: Without being unkind to poor Owen, if we want to sign someone who'll be unable to do a thing after five minutes on the pitch, I'm available on a free.
Scholes: Depends on which Scholes you're talking about. The player he was in his prime you don't replace, you just find other great players to build around. Maybe Sneijder'll be that player, maybe Rooney already is, maybe Nani will, but if we're talking the more recent Scholesy, Giggs is stepping into that role. Doesn't quite have Scholes' touch, but still gets forward better. Accumulates fewer cards as well. Which leads to:
Giggs: As he's not quite a winger anymore, Young steps into this role. Different sort of player, but we don't always need to replace an apple with an apple when the fruit salad will accommodate a pear just as easily. (That might be the worst metaphor I've ever written.) As for replacing Giggs when he finally retires, that's a problem for another year.