I have a little crown of thorns that I bought at the supermarket about ten years ago. It's a very low maintenance plant and it has pretty pink flowers all year (in our winters, the temperature usually only gets down to 0 C / 32 F), as long as it gets some direct sun every day.
It's a good stoical plant for garden beds you don't want to spend too much time on and it's a consistently good performer in terms of flowers.
Its drawbacks are that it's prickly and it has unpleasant white sap. It's also been very slow growing for me.

LOL I won't show a picture because it's just growing next to the compost bins. It doesn't do it justice, really.

Next to the compost bin! Tha';s funny.

But it's good to hear it's low maintenance. I already grow my share of prima donnas.

it's a very big genus - one I avoided for years because it was such a design cliche (along with phormiums). I do, however, have an enormous euphorbia characias

I've had my Euphorbia polychroma/cushion spurge plant 30+ years of benign neglect and it just keeps on truckin'. I planted it at the base of a tree stump where I lived 25 years, then dug it up and brought it to this address in 2006. In all that time I've done no more than admire it as I walk past it each day. It requires/demands nothing--I don't water it, feed it, prune it or attend it in any way other than to enjoy having it.

It has diminished in size since I planted it here but I assume that's an adjustment to dryer soil.

The 'Bonfire' cultivars I planted in 2010 are alive but haven't grown as large as they were when I planted them.

I grow euphorbia in mixed perennial beds along with Siberian iris, Echinacea, Shasta daisy, cardinal flower, clematis, peony, butterfly bush and others in full as well as part sun.

Euphorbia 'Chameleon' has interesting purple color, but needs to be cut back in early summer to prevent vigorous reseeding and to renew that purple.

I find I have had little luck with any except Robbiae and that is very aggressive. Someone told me that some euphorbias needed to (or did better) in containers.

Campanula, that is a gorgeous picture.

Gardenweed, I'd love to see a picture of that mixed bed. It sounds so pretty,

laceyvail, that's good to know since 'Chameleon' was one of the ones I was strongly considering.

shadyplace, I will take Robbiae's aggressive tendencies under advisement. Not sure I want to deal with that...

I have polychroma (bright yellow "flowers" in the spring) and a red one (not sure the name but it goes from purple to red with yellow... very pretty). The red one is right next to the step to my front door but its looking a little sad this year. Looks like out of nowhere it kind of heaved out of the ground a little and after the killer winter we had I think it did some damage.
Anyway, they're beautiful. I did pinch them back by about 1" when they're about 6" tall this year and they stayed nicely compact and didn't spread out in the middle even with all the rain we had (they did last year and got a little too big and leggy).

I grow euphorbia palustris (marsh spurge) in my moist/bog garden. It is currently 3 ft tall and would sprawl to 6 ft wide if I didn't cut back after it flowers in the spring. The spring show is very nice with large acid green bracts that last for 3-4 weeks. Fall color is also nice - orange- red. If you have the room and a wet spot I recommend this plant.

I have euphorbia bonfire. Completely shocked that it came back after late fall soaking rains followed the hellish winter. Looks healthy and pretty. Really like it, so far no sign of spreading like others have done.

I have E. rigida and E. myrsinites. they do not spread for me. They are a no care plant in a hot semi arid environment.

Polychroma sounds very pretty. And the red one is very intriguing to me, David, as the bed I'm thinking of planting inis gradually changing over to a red theme with some yellow highlights.

Felisa, I had never heard of marsh spurge so Iooked it up - what a gorgeous plant. Too bad I don't have anywhere appropriate for it.

Patty, I saw Bonfire over the weekend, which is actually why I was thinking of getting an Euphorbia! The only one the nursery had left looked pretty forlorn, so I passed, but I was impressed by the leaf color.

wontonamara (love that name!!), I am too cold for rigida. Too bad, it is quite lovely. I have to admit, I am too scared to try myrsinites as the sap is highly dangerous if it touched the skin. I happen to be very sensitive to poison ivy and while not the same; I don't think I want to find out if I'm sensitive to this one also!

Here is a collage of Bonfire in it's different stages in the growing season. Love this Euphorbia.
Top 2 pics 1 Coming into bloom....2 Bloom finishing and seed heads forming (notice how much color has changed)...Bottom 2 pics 1 All blooming heads in seed.... 2 Seed heads now cut back and new more deeply colored new growth has emerged.