I have had the opportunity to receive many shoulder strikes on the streets of Brooklyn and Manhattan (I call them "bumps"). Once I was knocked clean on my rear end in a crowd crossing the street in Times Square, ha!
The best thing to do, IMO is relax your knees and take it as far to the outside as possible (away from your heart). Then the bump will spin you instead of topple you, which is fine. It's calming down that's the hardest part.