Not too far from Wallingford is this little gem that hangs off a boatyard/marina and has some sweet riverside spots: http://www.portlandriversidemarina.c...ound/index.htm
Only downside - no sewer sites OR dump station so you need to head back down 91 a few exits to a rest area near Middletown to dump.
But the sites are large, the river is lovely and it's fairly close to Wallingford.
Much further away in the Quiet Corner (northeast CT by the MA border) is one of our faves in CT - an Army COE site on the Thompson dam. Really lovely.
Highly recommend the AllStays app for searching out new places. Let me know if you'd like more info. Good luck!