Butterfly Conservatory: Well worth the $$$ (and that's even reasonable)

Niagara On The Lake: Can be very crowded. Mostly small shops. Still a very pretty drive from NF.

Maid of the Mist: A must-do. Doesn't matter if you get on in Canada or US, the wait is small.

Clifton Hill: Touristy, but still fun. Casinos are nearby.

Toronto: If the Maple Leafs are playing, GO!

Stumble over to www.tripadvisor.com and you'll get some good info there.