When you go to Niagara Falls, make sure you go to the Canadian Side. American side has a walkway that will take you close to the bottom of the American falls which is pretty cool but there really isn't much else there. The Canadian side has a much better viewpoint for the horseshoe falls, paved walkway along the river, great places for pics, stand next to where the water drops over, etc.

On the Canadian side is the journey behind the falls (takes you into some tunnels behind the falls, and you can see the water rush down pas the end of the tunnel). Personally, I'd skip this attraction since you don't really have alot of time.

A walk up Clifton hill is also an interesting thing to do. One entire street going straight up this steep steep hill. Lined with wax museums, haunted houses, incredibly tacky touristy stores. Sooooo out of place next to a natural wonder. But, none the less, an interesting walk.

Maid of the mist boat ride is a must. www.maidofthemist.com The boat goes right up to the bottom of the Big Horseshoe falls, and you come out pretty wet (despite the rain poncho) but with some amazing pics. Great ride---something you MUST do! If you have time the IMAX movie also gives you a cool history of the falls & the stunts people have attempted. www.imaxniagara.com

All of the above are just on the other side of the border (Rainbow bridge I think), so it isn't far to go at all.