Do you have a photo you can post? It sounds like touch-me-not, AKA jewelweed and wild impatiens, although the ones I'm familiar with are much taller than 9" and your description of the plant growth doesn't fit. But the seed pods explode like that -- great dispersal method, isn't it? and great fun to surprise your friends with :) They may come smaller than the 2-3' I'm used to, or yours may be growing short for some other reason -- or I'm completely off-base on my ID :)

Flowers on the ones I know are yellow or orange. Also, the sap from touch-me-not is great against itching/stinging from nettle and other plant irritations.

Do a google image search and see if that looks anything like what you have. Someone else will probably know for sure.

Good luck!

Sounds more like bittercress to me. At this time of year they should be quite explosive and hurling their babies everywhere.

Here is a link that might be useful: bittercress info and image

I learned something new -- didn't know the mustard family had seed pods that exploded like that. Good catch, Kalmia!

Wow...I looked all over the web, and yes, bittercress is the closest thing to look like this weed. Thanks, Kalmia! It's got to be a close relative. The leaves only seem basal, and do not have any upward growth at all. But the seed pods are dead-on! I seem to be able to 'sneak up' on it, and grasp it gently from beneath, not disturbing it much as I pull it out. Thererore, not much of it seems to be in my yard (yet!) again. But my less fortunate friend, about a mile away, says his yard is covered with it again.
It's good to know your enemy! Thanks again!

Yep - now that I got a clue about its relatives, I think I found the actual culprit: Sorry I couldn't post my own photo, but will this do? www.psu.missouri.edu/fishel/smallflowered_bittercress.htm

Glad that I could help you put a name to that bugger. "Shotweed" is a common local name here (not to mention a few other names that would not be appropriate for this forum). I sort of admire its tenacity: its reproduction being aided by the very act of removal. A reference book I read described it as "spiteful" - good word. Once you begin yanking it in the early stages (late winter/early spring), you can really reduce the populations over a couple of seasons. There is hope. Good luck!

Shotweed! It certainly has the right nickname! It is a real problem in my garden this year...I don't remember seeing it before, or at least not this bad. It's everywhere and the seeds..even handling it gently, are explosive...good thing I wear glasses! Is there anything you can use on it? Seems I missed pulling them before it was too late. Thanks for putting a name to it...I appreciate the help. My weed book didn't have it listed.