In Port Macquarie itself there are a couple of art galleries, Flynn's beach, you could go Parasailing, or take a short drive to one of the vineyards (Cassegrain and Bago).
If you have transport I would suggest Trial Bay Goal, Arakoon lighthouse and a beach walk at South West Rocks.
Further out (about 1hr): Bellingen, the butter factory which has local crafts, opals and little cafe. Or chill out by the river. about 7 years ago
Little Fish Cafe at Innes Lake Winery is also really nice if you are into that kind of thing. Also, further down on The Ruins Way are the ruins of Major Innes' house and homestead. From the ruins you also get a fantastic view of Innes lake.
A walk along town green and down the break wall is also really nice. If you are feeling up to it, you can do the whole coast walk from town to the lighthouse.
On the river you can do jetskiing, from the pier in town, or if you go up to Settlement point, there is a great kayak hire place which is really fantastic.
The historic cemetery is also worth a visit. The gardens there are beautiful and the boardwalk through the mangroves. It is also home to some of the first settlers in Australia.
Markets to go to include the artist market at the maritime museum (opposite town beach) on saturday mornings and the markets at Westport high school on sundays or out on hastings river drive. They are all full of great local products.
About 30 minutes south of Port are the towns of lake Cathie, Bonny Hills, Lauriton and Camden Haven which are cute too.
I hope that has given you some inspiration. about 6 years ago