Garlic mustard.

Original title for this post: Could this be something called Malva? I saw a similar plant at a farmers market but didn't note anything but "Malva." There are a LOT of Malvi.

7/9/10 update: Top picture taken after all the violets were removed from the middle of the plant. Still waiting for a flower and still convinced this is something worth keeping (not just a violet).

3/1/11 update: Could this be skunk cabbage?

4/12/11 final update: Theora and Samohta-- see comments -- have convinced me that this is garlic mustard. It never seems to bloom but I think that's because the deer are snapping off the flowers before I ever see them. Related post is here.

Sheep sorrel, suggests Michelle. I think she may be right, but I need to see the flowers first. TBC.

4/12/11: Cleavers, Clivers, Goosegrass, Stickywilly, Stickyjack, Stickyweed, Stickyleaf, Catchweed, Robin-run-the-hedge or Coachweed

Little itty bitty white flowers.

I think brianheagney, see comments, has ID'ed it. These are all the common names used for this weed, according to Wikipedia. Galium aparine. 4/21/12 update: A new vote has come in. Patricia Newport (see comments) says this might be Galium tricornulum. I need to do some close examination to see which one it is. Does it produce 2-7 tiny white flowers OR 3 drooping tiny white flowers? This plant may be confused with other weed species of Galium, especially Galium tricornutum and Galium divaricatum. G. aparine has 2-7 tiny white flowers on erect stems up to 2.5 cm long, G. tricornutum has usually only 3 drooping tiny white flowers on shorter stems, up to about 1.5 cm long, and G. divaricatum, a more erect plant, has 3-12 yellowish red flowers. From here. The International Environmental Weed Foundation, in Sydney, Australia.