It's Euphorbia maculata.

Here is a link that might be useful: Google image results

Thanks, that looks to be it.

Does this stuff give anyone a rash? Like poison ivy? I am ASKING, not TELLING. Please don't start an urban myth from reading this, just trying to figure out what's giving me a rash, 2 springs in a row, and this is one plant I didn't ask about but I didn't know it was a Euphorbia until I saw this post. None left in my yard to take a picture of.

I apologize for the hijack, xsier!

Yes, I call it spotted spurge up north here. The milky substance that exudes from the stems are an irritant. I had a lot of this before I refurbished my lawns and gardens. It thrives on hot, dry weather like we had the summer of 2005 when I was trying to seed my new lawn.

I live (born and raised) in NW Florida, and have a
weed called 'bedstraw'. I just read this post, and
that reminded me that I had a rash from pulling this
weed. Pulled it for many years and had no bad results,
until last year. Now it gives me a rash.
I only have poison Ivy when I go to Indiana. I
wonder if PO left some residual poison, that is
now affecting me when I pull other things. As soon
as I come inside I use the rubbing alcohol on my arms.
Since this weed pulls easily, I have started putting on rubber gloves, to pull.

Nona, sensitivity to dermatitis-inducing plants can be transient, or develop over time, or subside. My neighbor says this year, for the first time ever (in 34 years) he can't pick figs, giving him an awful rash.

Regarding PI, I don't think urishiol remains potent outside for long, but away from the weather, many sources say it can still pose a threat after a year, on a shovel, jacket, etc...

Mysteries like these are no fun!