I think morning glories would work really well and you can find them started already in the nurseries, and it really is not too late to start those seeds, they are quick. I have also had good luck with scarlet runner beans, they move quickly too.

Helen

Black Eyed Susan Vine (in yellow or orange) goes crazy climbing and blooming.

Also you could try to find Purple Hyacinth Bean. Bees and butterflies love it. It's too late to start that one from seed though. (I had some seeds germinate 2.5 MONTHS after I started them.)

Why won't you try a perennial? (Just curious.)

I'm trying out Spanish Flag this year. It's in the morning glory family but sprays of red-orange flowers. It's supposed to attract lots of butterflies and hummingbirds.

-Marie

Malabar Spinach

Love-in-a-Puff

Canary Bird Vine (Tropaeolum peregrinum)

I second Spanish Flag -- only a part of each flower is red and the overall impression is not red.

I'd second the black eye'd susan vine.
I've had them in window boxes that occassionally forget to get watered. Find them almost crispy, water, and within a half hour they are good to go again. Very forgiving plant.
Also, I just started my seeds this weekend, so it's not to late :)

I'll be bringing a bunch of Japanese Morning Glory seedlings to the spring swap. The person I got them from in a swap collected seeds from plants of seed she ordered last year so we may get something really nice or ho hum.
If interested be sure to come to the swap next Sunday.
Will