In reply to The Lemming:
1) Boat trip to see the seals from Morston Quay, some boats will drop you off for a wander around Scolt Head. Search for Blakeney Seals and you'll find a couple of local companies offering trips.
2) Norwich Cathedral is impressive if you like that sort of thing, there's also Norwich Castle to visit and the parts of the city away from Castle Mall and Chapelfield Mall have a good range of interesting small shops.
3) Holkham Beach is good for wide open space walks, in fact most of the North Norfolk Coast is really beautiful and a mecca for bird watching.
4) Sainsbury Centre for Visual Arts on the UEA campus
5) You can hire canoes from The Canoe Man who also supplies maps etc
6) Thetford Forest has some good Mountain Bike Trails, there is a Go Ape there too
7) Personally I think I'd drown myself if I had to spend a week on a Broads Cruiser, there is a 4 knot maximum speed and much of the scenery is reeds, and reeds, and reeds but then I live locally so am probably terribly biased.
8) If you've a mind to climb there is Highball, an impressive bouldering centre near the Airport, there is climbing at the Sportspark at UEA but for a short visit I don't think it's worth the hassle of trying to climb there.
9) Norwich itself can be a pain to drive through, there is no decent ring road so I would base yourself either North or South of the city depending upon what you think you'll be doing mostly.