How about some large leaf cannas like musafolia canna or red stripe? Plus you can harvest the seeds and re-grow them next year.

Oh,and duh...you can dig the rhizomes and get a jump start on next year.

Some of the passiflora vines are hardy but they can become invasive as well. P. incarnata, incense and caerulea are some of the ones that are hardy in my zone (7a). There's also cold hardy bananas but they don't produce fruit.
Karyn

And where do I get canna musafolia seeds :)? I guess I should have ask for suggestions on who to order seed from. Thanks a lot

Cannas are not going to grow fast for you from seeds, even if you feed it manure and fert everyday. What you need is the rhizomes of the canna.

Also look into castor bean plants, they are fast growers, by the time we get to Aug, you can be looking at a 8-10ft giant.

Checkout my castor bean and other plants in the link below

http://www.ubcbotanicalgarden.org/forums/showthread.php?t=40574

I find heat to be the trick for fast growing cannas from seed. My seedlings sat not growing much at all until our spring nights gave way to summer temperatures. Then the canna seedlings took off. They probably will not bloom until next year though.
You can also try some palms from seed. Needle palm, pygmy Date palm and cocos palms all grow fairly fast from seed and they are hardy in your areal. Hope this is helpful. Linda

Or you can do elephant ears

glaswegian: Your castor beans are huge. Do you start them from seed every year? What variety? They are beautiful. Thanks for the pictures. Castor beans are exactly the type of plant I am looking for--fast growing, exotic, and easy to start from seed (If I could just take a break from taking things into my garage :(
Ibartoo: Are all those hardy in my area? And, where does one get the seed? Thanks again

I started the castors indoors in the basement under growlights in early March. There is a 100% germination. The variety I have in the pic is

Castor Bean 'Carmencita Red'

I also have Castor Bean 'Zanzibariensis' which grows to 15ft in the backyard

About the Passiflora that someone mentioned in an earlier post...I just plunked some pieces in a glass of water, and it worked. I'll be taking cuttings this Fall, instead of hauling yet another plant in for the winter. I have to keep stuff alive in my dining room over the long, frozen winter here in Wisconsin.