My husband and I love periwinkle (vinca minor) as a groundcover. It is very manageable, grows well in dry shady sites, looks great under trees, prevents weeds and the blooms are just lovely now in the spring :)
We also have the variegated version (vinca major) and that doesn't seem to have as many blooms and is in my opinion invasive, I'm always yanking it out so it doesn't take over!
I have Vinca minor and like it, though I wish I could get more perennials to grow through it. I have it in a shade/part shade area. Another shade (to full sun) ground cover to try that has a good bit of color is Chameleon Flower. It thrives in zones 5-8, is 6-9" tall and gets dainty white flowers. The foliage has reds, creams and tons of variegated green colors. The markings remind me of a hosta but more color obviously. I saw a bed of this and loved it because it put some color into the shade. It is a ground cover, so like the others it will probably have to be watched. I've had it for two years now and still enjoy it. In fact, I wish that I had bought more so that it would be more filled in now.
I'm in central Texas and looking for a nice groundcover to butt up to a walkway. It'll be in a mostly shaded area under dwarf nandinos so I'm looking for something with a yellow or red flower. Looking for something that will spread nicely but not take over. Any suggestions?