Thats what I was thinking too.  White clover?  I may just overseed the entire yard and have a mix of grass and clover. I have read that both thrive when mixed.
I think I missed the time to plant it this year.  I may do that next winter for the frost seeding season in late January.  I have some areas to prep anyway because they are fairly overgrown.  I will slowly get those hacked down (weedwack and then lawnmower when low enough since I never did get that tractor 

) over the summer in preparation for winter seeding.  I've been keeping an eye out for a nice used rough cut mower locally.