Looks like it may be: Portulaca oleracea - Purslane

I think that is one of them!
I haven't seen the little yellow flowers (yet), but I'll keep looking.
Wikipedia has some interesting things to say about it:
http://en.wikipedia.org/wiki/Portulaca_oleracea

What about the other one?

thanks for help!

Sorry, I just looked at the pictures quickly and thought they were different views of the same plant :)

Upon closer inspection I see they are indeed different. It looks like Common knotweed, Polygonum arenastrum.

yuck!
"It is also a host for other weeds such as beet curly top, and for viruses such as beet ring spot and powdery mildew"

(thanks for info!! I'm having so much fun working on my backyard! Me and my two brown thumbs... heehee)