My husband and I are planning a week long trip this summer to include several days in Quebec City and several days in Vermont. We were thinking of flying into Quebec City, driving to Vermont and then flying home to Pennsylvania. We would appreciate hearing from anyone who has made this trip with suggestions for driving routes, places to stay, things to see, etc.

You will not be able to rent a car in Canada and return it in the US. Pennsylvania is close enough to drive up I-88 through Albany and I-87 to go through Montreal.
The other option is to park in Schenectady and ride the Adirondak Amtrak train to Montreal and take the ViaRail train to Quebec City. Whichever way try to drive your own car at least partway. Where do you want to go in Vermont?

Thanks for the information. In Vermont, I was thinking about somewhere near Burlington since there's an airport there but maybe we would be better off doing Montreal and Quebec City instead of Quebec City and Vermont.

I live in rural NH about 5 miles from Vermont, and I visit Montreal and Quebec City frequently. You have to decide what you want in a vacation - Vermont is vastly different than Quebec City or Montreal. Vacationing in Vermont is about being in a rural environment - hiking, biking, swimming, etc. Burlington is a nice little city, but shouldn't be the prime reason for visiting Vermont, which has some incredibly beautiful countryside. Vermont is about relaxation and the outdoors.
Montreal is one of the most hip, cosmopolitan cities in North America - fantastic dining, street life, shopping all with a European flair. Quebec City is very charming, very French, and unique on this side of the Atlantic. Rural Quebec can also offer some great outdoors opportunities, but has a different vibe than Vermont. Check out the bonjourquebec.com website for lots of info on Quebec.
You could fly into Burlington (probably cheaper than flying into QC), rent a car in Vermont, then drive up to Montreal and or QC (easy drives), and fly back out of Burlington.

If you've not been to either Montreal or QC before, and you're from PA, you should probably alter your plans to fly to Canada, rent a vehicle in Canada, and see both of those cities.

There is only one state between PA and VT, and you have plenty of time to get up that way at a future point.

IF, by chance, you fly into and out of Montreal, you might even be able to dodge needing a rental car for part or all of your time in that city. Mtl is a great walking-around town, and you could stay at mid-town and get a lot covered. (and MAYBE even save more money on a car rental by avoiding having to get the car at the airport.

(no doubt you'll need the savings for GAS)

I like the drive along the St. Lawrence, to QC, especially when getting off the main freeway and taking the smaller highway through towns on the north shore of the river.

Surely you'll have a good time up there no matter which choices you make!