Nobody's mentioned passiflora, commonly known as Passion Flower. This is a gentle soul, and has the advantage over clematis in being evergreen.

We planted an 18" sapling of this against a tatty hedge back in June, and it has grown to about 6 foot by 5 foot across, completely covering a large hole in the hedge. Never seen anything grow so fast, and need so little attention (apart from guiding its growth directions of course).

It also has nice little white & purple flowers as an added bonus.