I know that one of these is a Barred Rock and one is a Black Australorp, the third is probably my Meyer Hatchery Meal Maker (aka random chick male or female). Of course I can just wait and see, but I like the idea of trying to figure it out and see if we are right! The one on the right (C) has no head spot, so I was thinking she is the Australorp and the other two are Barred Rocks, but then all three have eye markings.
Here you can see that the spot coloration is different, A is definitely more yellow (and larger) than B.
The one with the whiter spot (B), on the far left in the photo, also has a more distinctive comb than the other two.
For reference these guys were supposed to have been hatched on January 7th.

Generally speaking, they're not going to send rare, expensive breeds for free.