How about clematis? There are many varieties (like Carnaby and Blue light, and many more) that do well in containers, and are supposedly hardy to zone 4. Try the link at the bottom of this post for more info. Hope this helps!

Aimee

Here is a link that might be useful: clematis info

What about Trumpet Vine or native honeysuckle (Lonicera sempervirens)?

I planted a couple of native honeysuckle, last October (they were marked 75% off) and they are really lovely plants, they were semi-evergreen all winter. But I could tell from the craggy texture of their slender bark runners that they'd be interesting even if they had lost all their leaves. Its been flowering since Spring. (I have to confess its in a sunny hot spot.)

I also bought Trumpet Vine for 75% off. It died way back and is just making its comeback. No flowers yet, but its in a much cooler and less sunny spot than the native honeysuckle.

Do the planters have a bottom or are they just decorative with the earth down below? If they're just planters, you might not be able to get a perennial to winter over in the planters--perennials usually need the protection of the ground to wintering. If the plants can get to the earth (and the planters are really just decorative four sides with no bottom), I'd plant climbing roses.

Like the following two perhaps:
http://www.ljplus.ru/img2/pycaky/Climbing-Roses.jpg
http://www.plantsplus.com.au/cmsimages/2.climbing_rose_2.jpg

Or any others you like. I find roses very easy to grow. I was always afraid of them--thinking they were difficult. Then I moved onto property with rose bushes. They took care of themselves. So I got daring and bought some new ones. They're doing great too!

Have you thought about Purple Hyacinth Bean Vine? They are not perennials but are easy to grow and they grow quickly. I think they are beautiful and once you plant them they will reward you with tons of seed each year so that you can easily keep them going year after year.

Perennials do fine in containers. You would want to look for one that is hardy to 1 - 2 Zones lower than where you are. I have several including some of what was previously mentioned (hardy to Zone 4/5) like honeysuckle (L. x mandarin and L. sempervirens 'Blanche Sandman'), Wisteria frutescens (american wisteria), & clematis ("Prince Charles").

For the clematis, you might consider looking for one of the group 3s which would allow you to cut it all the way back in late winter to about the lowest couple pairs of buds. Then you won't have to worry about possibly losing previous-season flower buds in a cold winter, which could happen with a group 1 that's not protected.

Actually going to suggest a wisteria. Lest you think I'm crazy I suggest Wisteria fructescens, this is an American native wisteria, and not nearly as aggressive as Chinese wisteria. Also, it has a habit of blooming large in spring, and continued smaller rebloom cycles throughout most of the summer.

George

geoforce, is Wisteria Fructescen light enough to grow on porch structures?

I absolutely love wisteria but avoided it because I heard that it can do structural damage. I'd be very happy to learn there's a wisteria out there that's less aggressive and doesn't get so massive.

Maggie - it will still get massive over time but it does not grow as fast as the asian wisterias. Plus since the American one blooms on new growth, you can prune the heck out of them. Also they bloom at an earlier age, which means blooms when smaller. The only drawback is that it doesn't have the sweet fragrance of the asian wisterias.