Posted: 05/06/2014 at 14:51
The Euphorbia in the very first photo is Euphorbia helioscopa, Sun Spurge.
In the recent set of photos, the top one is Shepherd's Purse, Capsella bursa-pastoris. The middle one is a bitter-cress, you need to count the stamens to be sure which one you have. The bottom one is Creeping Buttercup, Ranunculus repens.
They are all weeds in the garden, spreading prolifically. Get rid!