Some see weeds...

I think it's a matter of perspective.

J.A.Y.A. (Just Another Yellow Asteraceae)

Crupina crupinastrum (Crupina)

Adonis palaestina (Palestine Pheasant's Eye)

Tesiera glastifolia (Globe Mustard)

(I think--you really need the fruits to identify these, and they haven't matured yet.)

Trifolium resupinatum (Pink Clover)

The first three beauties were found on a field trip with my biology class of three high school guys; they're not completely past the "they're just weeds" perspective, but they're coming along and can now place some common wildflowers in their proper families. The mustard is growing in many a vacant lot and field around town, including the one across from our house, and the clover is a mostly unnoticed "weed" in our front yard.