http://www.silverstarvinery.com/

This is a good source for clematis and gives blooming times.

I have one clematis (Josephine) that does spring and autumn (but not as big a bloom in autumn).

I have planted 5 this spring so we will see how they do.

Mind you I only have two kinds of blooming size, but of those Dr. Ruppel (spelling?) seems to bloom nicely for me most of the summer/fall. We've had it for several years and it Has a typical 1 or 2 good shows but then continued to bloom sporadically as well. It also grows faster than my Jackmannii.

Squirrellypete

This site had some interesting info that may be useful:

http://hummingbirdfarm.net/clematis_varieties.htm

This Etoile Violette blooms for about 3 or 4 weeks and then is taken over by the Clematis viorna which blooms from spring until late summer. You can see the C.viorna coming up to the top in this pic. Not sure why my camera seems to make the Violette so blue, they are more purple than they look here.

Vroomp,
Your clematis are gorgeous! Where did you get C. viorna? The Violetta seems more vigorous than the other, is that a problem? or not?

My longest blooming clematis is C. texensis. But you trade a momentary, big show of a hybrid for its long, sporadic bloom time. Clematis texensis blooms all summer. I love it though. It seems more heat-tolerant than the others.

I actually "rescued" my C.viorna from an area around the Chatahoochee that was being developed. All attempts to start seed or start new vines from layering have failed. I plan to use another method this year in my attempts to propagate this one.
Having them compete for space doesn't seem to matter to these vines. The viorna has a longer growth period.

I have heard that Huldine will bloom all summer long. It is very pretty with stripes on the back of the blooms. I am looking everywhere for this one!

gorgeous blooms vroomp. I think it may be your computer monitor that makes the purple appear more blue because on my computer they look true purple. Does anyone know of a more blue clematis? I would love to find one with blue flowers.

this one can appear blue in certain lighting but it really looks like a shade of purple/lavender most of the time.
'blue ravine' is blooming now but does not repeat during the growing season.
i like it anyway. ;-)

Hello, Kathyga:
There are several that are nice blues, but the "Belle of Woking" is my favorite. It has gorgeous, doubled blue flowers. They look like huge zinnias. I think I saw a picture of some while in eBay the other night.