Can anyone identify these pretty blue flowers?

http://www.wildfiregroup.com/flowers

They grow in my backyard in Boston, MA.

They come up in the very early spring in clusters, and last about a
week or so before they flowers die off. They look like clumps of grass
when the flowers fall off.

If you dig them up, you find small bulbs that are really easy and fun
to transplant.

I've been through a number of plant identification books, and I can't
find them.