http://www.stepables.com/
Main site
http://www.stepables.com/store/scripts/prodSearch.asp
Plant serch by region, soil, water, traffic, sun, etc, etc.
These plants are sold at many nursey's but what I like about this specific brand is that they give you all the details. How much traffic they can take, water/ sun requirments, etc, etc.
I love, love, love the creeping speedwell. It is an amazing ground cover that is super hardy and very nice to look at as well. Ours is flowering right now, it's almost as if it was frosted with snow in our front yard.
Once you decided on a specific kind then you can search for more local sources or seeds. Although we purchased this brand at a local nursey. On this website you can search for local nurseys in your area. It was pricey, but has the different kind of ground covers have grown at different rates, the creeping speedwell is a fast grower! We started with 6 plugs basically, about a styrofoam cup size and we could dig it all up now and have over 200 sytrofoam cups, not bad for 2 years.
Good luck.
We also have several other ground covers some are more hardy than the others, I can look them up if anyone likes and provide pictures if desired.