We're in Zone 7b... actually, literally straddling the line of zone 7 and 8, and quite a few cactus species can survive outside here. Of course, we get more rain than the dessert, so good drainage is essential.
here's some pics...
Echinocactus texensis... AKA Texas Horse Crippler or Texas lace cactus... native more or less to this area... this is a very small plant that will eventually get about 8 inches across and 3 inches tall... more or less a spiny pancake. Each cluster of spines has a center spine that is hard as a nail and is quite capable of crippling a horse, and there are stories about them flattening tires and going through the sole of a boot. They present a certain amount of danger to cattle, and for this reason ranchers habitually kill them on sight. Consequently, they're more or less endangered in the wild. If you start at Ft. Worth, draw a line straight south, and another line straight west, that southwestern wedge is the native territory of the plant. This is a seed grown plant from the wonderful people at High Country Gardens, and is several years from being big enough to bloom...
Echinocereus reichenbachii v. baileyii Baileys Lace Cactus... got this little guy off ebay, since I planted him outside, he's started to develop buds... I'll be sure to post pics of the blooms, as they're bright pink and bigger around than the plant. Native to Oklahoma, there are reports of the plant being hardy up to zone 5. Easy to handle, the spines are actually soft, and you don't notice it too much in the pic, but the center new spines have a definite pinkish look.
Echinocereus triglochidiatus Claret Cup Cactus, White Sands Strain. This Claret Cup is evidently going to become much bigger than the normal plants, The guys at High Country Gardens say that it can reach 2 or 3 feet tall, and have small offsets to about 2 feet wide. Right now, it's about 2 inches tall, and I don't really expect to see any of the bright red blooms for at least a year, possibly longer. Hardy to zone 5... so it should do fine here.
Escobaria missouriensis... Missouri behive cactus.... a rather common northern species, native all the way into North Dakota, and some reports of it being hardy into Canada. This has bright yellow blooms. I also aquired this from the great people at High Country Gardens, and it's small yet, less than an inch tall and a little more than that wide. They're rather quick gowers, usually not getting more than 3 inches tall, but making many pups to form mats of blooming spines... don't know if I'll get blooms this year, but it may start the offset sometime this summer.
Mammilaria meiacantha Pincushion cactus. This came to me from Home Depot. Tag said it Mammilaria 'species' and guaranteed to be hardy to 20 degrees farenheigh. I'm 99% sure that it's a meiacantha, and it should be hardy up to zone 6, but I'm waiting for the blooms to make sure... I know that it survived outside in a pot this winter, and since it's 5 inches in diameter, it's more than large enough to bloom this summer.
This came from Home Depot also, Echinopsis 'species' supposedly hardy to 20 degrees... This is really why I don't like buying from those large chains... you never really know what you're gonna end up with... don't even have a tentative idea of what the species is, so I'm waiting for a bloom, but it might be a hybrid. Again, it's big enough to bloom, so we'll watch it this summer.