Fronts:
VW Golf Mk6
VW Scirocco
Audi A3 (8P)
Audi A4 (B8)
Audi A5
Audi TT (8J)
Audi R8
I think B7 A4 seats might be a straight swap as well.
Bear in mind that for any of those options the airbag will most likely not be suitable, so none of the options will fit "without modification"
Finally, I'm led to believe the rears for the Audi A3 and Golf are completely interchangeable.
Best of luck. What did you have in mind?