By boat in town
Arendal's town summer life extends to the sea. Indeed it is hard to say if sidewalk promenading or harbour cruising is the most popular way of seeing end being seen.
Locals often use boats to go to town, and "park" along Pollen bay or other parts of the harbour. Not exactly Venice, but nice to watch.
My dad was from Arendal (a town/city in the South of Norway) so I visit my grandmother every summer. She used to live in a little place right outside the city of Arendal, called Eydehavn (named after Samuel Eyde of "Norsk Hydro").
She has now moved into Arendal, but we still go out to Buøya every summer to bathe and have fun. Arendal is (to me) a summer city, I am almost never there during the winter, but it is definately a pearl of Norway.
Forest, sea, sun and beautiful scenery, as well as history and tradition.
I recommend i hotel in the center of the city and at least one guided boat trip from the "Pollen" (it's in the middle of the city, you can't miss it). Try a tour to "Merdø" an island a couple of hours slow boat ride out. THey've got good mackerel and a little museum. If you don't fancy museums a walk around the island is lovely.
This year (2006) my cousin got married in Arendal and so we attended. My mum and me stayed with my grandmother and we had another lovely week in the summercity of my childhood ;-)
The father of the bride arranged a boat trip the day after the wedding and it was excellent. Lovely weather made the day splendid. We took a tour around the islands and got a tan (some of us got a bit burned...).
Nothing more to tell really. If you're planning a visit to Norway (in the summer) you should stop by. It's got loads of perfect fish, nice, friendly people and ice cream. Culture too, it's just refurbished the city's cultural center. As with eveything in Norway it might be a bit expensive, but since I never stay in a hotel while I'm there I can't really recommend any. The tourist information is right in the center of the city too though and they'll guide you.
Norway is a beautiful country and what you have to see is the coast-all the way around. It's amazing, very clean and the towns are so charming. I've had a great opportunity of visiting the South of Norway - especially Arendal but I hope I'll get back there one day to visit some other parts of this beautiful country.