In general, my favorites are the viticella hybrids because they are easy to grow and even though they have smaller blossoms, they have a lot of them. Also, in my climate with a long and hot growing season, I can get rebloom on them, but I don't know that this would be true in your colder climate.

Little Nell - lots of cute little white flowers with mauve edges - a good contrast for darker colors

Maria Cornelia - white flowers with a somewhat unusual shape. It is only a year old and hasn't bloomed as much as some new ones, but still more than some others.

Little Bas - just masses of blooms with a dusky purple color and wide open bell shape

Galore - very fast to establish for me - nice somewhat dusky purple color that is vibrant, but still soft looking - not as red as Etoile Violette

John Howells - new for me, but already has nice red blooms with a white reverse

Pendragon - a real energizer bunny (just doesn't stop blooming), but it does tend to get naked legs (could partly be from a location pretty close to a large pine tree). It is a reddish purple bell with a shape similar to Betty Corning - flower size and color varies a bit with the weather

Emilia Plater - by far the most vigorous for me - I just moved it from its prime spot to a not as nice location because it was just too large for the spot it was in. It has a pale violet blue color that really glows in the dusk, and had at least three bloom periods for me.

Prince Charles - pale blue color similar to Emilia Plater, but a smaller growing vine

I also like some of the non vining clematis which I grow with support, although some people just let them scramble:

Zoin (aka Inspiration) my first non vining type with pink flowers. It probably blooms more for me than any other clematis I have - there are very few time periods when it doesn't have at least a few flowers.

Petite Faucon - I really like this even shorter growing one. It has dark purplish blue flowers and repeats well, often having both large seed heads and flowers at the same time.

Juuli - I added this one partly because it was highly recommended by others on this forum. It has lots of really nicely shaped flowers in a medium lavender blue color.

Hi there! I don't have jackmanii but have heard great things about it. I love love love comtesse de Bouchard soo very much. It blooms great and is the perfect color for me. I also have Madame Julia correvon and it is an excellent bloomer . Pretty much non stop once it starts!
I just planted ville de Lyon last week. I love the color and shape of the flowers.
I did not have luck with blue angel, I loved it but it wilted and never returned.
Good luck!! Please post pics if you can!

It definitely depends on your personal taste, but I also prefer viticella hybrids, and the species as well: http://www.gardenvines.com/shop/small-flowered-clematis-4/clematis-viticella-228.html

I grow ~20 different varieties, and Betty Corning is my favorite for how long she blooms in my area, and also for her beauty and fragrance. I have one by our hose bib just outside our breakfast nook and get whiffs of her all day long. I think the smell is SO delicious and perfect. My husband can't smell it though, so maybe the scent is too subtle for some people. I planted 2 more along our front porch a couple of years ago, but they are north facing so take longer to get going.

Venosa Violacea is also really fun one. Mine is still getting established, but I really like its coloring and flower size.

Another one that I think is beautiful is Viorna, but it wasn't doing well in the too shady spot where I put it last year so I recently moved it and will see if it does better.

There are so many beautiful clematis. I would just plant a few that look beautiful to you and give them a try in your garden. They take awhile to establish and take off, but are definitely worth it!

So the ones I have so far are: Jackmanii, Ville de Lyon, Comptess du Bouchard (not Nelly Moser), John Paul II, Crystal Fountain and a NOID (with a very different leaf structure). I've told my husband that we're looking to also get some more based on your recommendations: John Howell, Little Nell, Betty Corning and Inspiration. I also have seen a few others on here that I have fallen for: Arctic Queen, Still Waters, Guernsey Cream, Twinkle and Temptation. I'm already a hosta collector and a daylily collector. I can easily see this becoming my next "thing".......I have space on my mailbox and I have some rails in the front yard for them, a lilac shrub or two or three, a WHOLE shed to cover......and a few new trellis' going in this year.