In reply to Matt_79:
Yes, I used to run a company in Shetland - Shetland Walking and Wildlife. Ronas Hill is a great one - easy if you climb it from the radio masts car park on Collafirth Hill, but a bit of a bog slog if you do it from the head of Ronas Voe. For a great day out head west from the summit to Stonga Banks, and then down the fixed rope to the beach at Lang Ayre.
The walking on Foula, and out on the Westside is also superb.
Shetland is more Norse than Scottish, and no you can't see Norway from there (or Iceland, or Greenland!).
Enjoy your trip.
Graham