Tiny purple/blue flowers.

White spires

Final one, lavendar blooms

The final picture with lavender blooms is some kind of knapweed, maybe spotted. Definitely get rid of it.

'White spires' are Melilotus alba.

'Purple/blue flowers' are indistinct but check Medicago sativa.

Top one compare with Berteroa incana.

Thank you both! You were right on all accounts!

#1 - Hoary Alyssum (Berteroa incana)
My entire back yard is coated in the white flowers before I get a chance to mow again! Almost more white than there is green! This is a perfect photo of them:
http://www.francini-mycologie.fr/BOTANIQUE/Berteroa_incana.html

#2 Alfalfa (Meidcago sativa) - This guy isnt so bad, he stays within the bounds of the field. I just always wondered what they were.
http://michiganflora.net/image.aspx?img=2116&id=1332

#3 - White Sweet Clover (Melilotus alba) - Not a bad problem
http://michiganflora.net/species.aspx?id=1333

#4 - Spotted Knapweed (Centaurea stoebe subsp. micranthos) - This is the second most prominent weed in the yard. I am in michigan and have sandy soil. I guess this is a statewide problem.
http://nativeplants.msu.edu/restoration/spotted_knapweed

And thanks to both of you: I found the following for help identifying any more I encounter! (Shared incase anyone else stumbles on this).

http://www.invasive.org/
http://michiganflora.net/