All of Ærøskøbing is comprised of quaint buildings from the 17th Century... except for the Netto. This supermarket, located within sight of the ferry dock, has a large selection of groceries at reasonable prices (by Danish standards). Great for picnics, and/or if you have accommodations with a kitchen. Open Monday-Friday 9AM to 7PM, Saturday 8AM to 7PM, closed Sunday.
There are two shops to buy food in Aeroskobing - lower price shop Netto (you can see it when you come by ferry) and Spar (in the main square of the town). If you want to taste locally made cookies and pies, you can try it in the main street - Vestergade. Also the shops of other kinds are also mostly located in Vestergade - there are 3 shops to buy discounted used goods or antiques (they are very popular among turists and danes, sometimes you can find great old things there!). For those wishing to buy souvernirs, postcards, flowers, toys and alike the shops are also located in Vestergade. There are several shops for clothes, home things - street Sondergade. But the area is not so big, so you will see all the shops yourself for sure! However if you go just shopping, it is better to do it in Svendborg or other bigger town, they have more variety and better prices. Also lot of of shops in Aero close for non-summer season.
Ærøskøbing is a small town but there are some specialized butik and a branch of discount supermarket Netto. That makes you spend less even tho you are a little far from the mainland Denmark.