I find the run from from Cape Cod canal to Gloucester to be a decent day's sail. I usually drop the hook in Onset for the night since there really isn't a good place near the northeastern end of the CCC. Depending on the current you either have to leave near dawn or can laze about for part of the morning before getting underwayMake sure you have Eldriges or some other reliable current table. As long as you miss the middle four hours of the foul current you should be OK if you have a reliable engine (you can't sail through the CCC, you have to go through under power). From the CCC it is an easy day's run to Gloucester or if you get underway real early you can make Isles of Shoals before nightfall.
Gloucester, is a convenient run from Onset. We didn't find Gloucester that fascinating, so might try Marblehead next time instead. Or we might simply head straight for wherever in Maine we wanted to go. Freeport's main attraction seems to be the shopping, rather than the harbor. Getting further East is probably more interesting than heading to a series of outdoor outlets strung along a busy street. We liked Stonington, on Deer Isle, Blue Hill, and Little Cranberry Island. For towns with amenities, Belfast and Portland are worth checking out. Camden, Kennebunkport, and Boothbay were crowded with tourists who, judging from the numbers of stores pushing them, only buy t-shirts. The best blueberry muffins anywhere come with meals at the Dolphin Marina Restaurant in Harpswell.