What is this?!
Pictures one and three show a perennial groundcover in the sedum family. It will bloom eventually and helps keep other weeds down, but can become weedy since it spreads so vigorously. It is easy to pull though.
The second photo is the weed called hairy bittercress. They are easy to pull so get them now because once those flowers drop and seeds ripen, any little nudge or breeze will send them exploding nearby and you will have more next year.
Here is our page on it: http://extension.umd.edu/hgic/topics/hairy-bittercress