Especially if you haven't been in the area before, I'd suggest you go island hopping. Maybe the greatest thing about Stockholm is its archipelago. It's special in the way that's there are thousands of islands, some quite big, others very small. It's truly beautiful. There are boats you can take from central Stockholm (commonly called "Waxholmsbåtar" - Waxholm boats) that take you to just about anywhere in the populated part of the archipelago.