For some reason, this makes me think of plumbago. It comes up late in the spring, but works well with bulbs. The flowers are electric blue, and it has very good fall color.

Sarah,

I have heucheras in full sun and they are gorgeous! I think that if you go and read labels you will see that some actually have full sun on the label..

I have a frosted violet that is very large and in full sun that's beautiful all year! I can check the names of the others if you want to know.

Lisa

how big an area are you trying to cover?

perennial or shrub? if shrub, evergreen or deciduous?

one of my favorite evergreen groundcovers is paxistma canbyi. No flowers, but adorable trouble-free foliage and not aggressive.

Doesn't sound like enough sun for roses. However, my 'The Fairy' groundcover roses get a bit more sun than that and flower well.

some dwarf azaleas? If so, have to watch out for the hardiness though. Some of them might be finicky to bloom. I have a couple that do well here.

Here is one of my favorite links on the subject. Haven't read it in a while, but I used it a lot.

http://forums.gardenweb.com/forums/load/neweng/msg0819161830992.html?12296

Knowing the width of space you have to fill and some information about your goals for the area would be helpful. Are you looking to fill the area with all one kind of plant or do you want some variety? Is it surrounded by pavement that will restrict truly vigorous spreaders or does it border a lawn area? Are you looking for something dense enough to choke out weeds? My Annabelles do some spreading themselves, so I don't think you need to worry about the more aggressive groundcovers on that side.

I have low-growing groundcovers (6" or less) Veronica 'Georgia blue' (blue-purple flowers), Arenaria montana/Sandwort (white flowers), Dianthus 'Graystone' (white flowers, gray-silver foliage, though other Dianthus varieties have bright pink flowers), myrtle/periwinkle (blue-purple flowers), thyme, Geranium 'Jolly Bee' (blue-purple flowers), Vaccinium macrocarpon/cranberry (tiny pink flowers and reddish foliage plus handsome red berries in the fall and winter). The last two are looser plants and need mulch under them to prevent or reduce weeds, but the rest are quite dense. All grow well in full sun to at least part shade.

I also have a few taller plants that I grow as ground covers. I have Carex 'Ice Dance' with striped grassy leaves and unobtrusive flowers, which is 8-10 inches tall, though the voles decimate it every winter. I also have a steep area that I didn't want to mow, so I planted it densely with orange day lilies and mulched it and maybe spend an hour or two a year maintaining it, weeding and renewing mulch a bit. The plants have spread to fill the area completely. I have a double mum that I have no name for that spreads vigorously enough to need taming every few years and has beautiful flowers that are a mix of orange, pink and yellow, but at a short distance read as a coppery color. It chokes out weeds completely and blooms all fall until a hard freeze. It often blooms right through the first few light snows. (If you want a hunk, feel free to come get some!) I also have a spreading low-growing mum, Chrysanthemum weyrichii 'White Bomb' that is about 5" tall most of the year and has 8" daisies in the fall. I find that Nepeta (blue-purple flowers) grows densely enough so that no weeds grow into it and a few plants will fill a medium space well, though it doesn't spread.

You mentioned Heuchera as a groundcover. I don't find that mine really spread and they need dividing every few years, but I find that they do a good job of keeping down weeds where they are relatively densely planted.

Here's a different idea that I'm trying in my small front garden: rhus "low grow." It is a groundcover sumac, and will have wonderful fall color.
Here's what I observed so far: it is late(r) to leaf out. The mt.airy fothergilla are just blooming, and the rhus is just breaking bud. It is woody, which may make it difficult to clean the leaves out of its branches. On the other hand, if it is sufficiently dense, that may not be a problem.

Find some good pix on the web.
Tell us what you decide!
idabean