It looks like Quack grass. The best way to get rid of it is by using some RoundUp on it but be careful to not get the RU on any of your desirable grass.

I'm hesitant to use something like roundup, as there's a mixture of the weed and desirable grass. Not sure how I would kill only that. I'll go to a local nursery and see if there's something more specific that won't kill the good grass.

If you do not want to use RU I suggest you dig it up by hand and also a good 6-8 inches of soil with it and start over with new soil and seed.
Good luck!

This post was edited by slick2211 on Fri, Apr 11, 14 at 20:44

If you have broad leaf weeds like dandelions growing in among grass, then you can use a herbicide especially designed for broad leaf plants. If you have grass plants growing in your flower garden, then you can use a herbicide designed to kill grasses. But if you have grassy weeds growing in grass, you either have to dig it all out or take the tough love approach (Round Up). There are a very few grass specific chemicals. I don't use them but hopefully someone who does will come and help.