Grape hyacinths and chionodoxa.

Susan's suggestions are great. They are hardy to zone 3, will naturalize, are good for sun/part shade, are less likely to be disturbed by critters, and are early bulbs. You won't be able to control when the groundskeepers cut the grass, so it might be best to look at the earliest spring bulbs. The early spring bulbs will have time for their foliage to store enough energy for next years growth before the first mow. I'd add crocus tommasinianus to the list of contenders.

Over Thanksgiving, I planted Crocus tommasinianus over my mom's and grandparents' graves. I looked for something early and short and that had a good chance of naturalizing. I read that other crocus species and hybrids tend to peter out in lawns, but that C. tommasinianus had staying power.

Since I am a couple states away, I kept a few to remember them and also know when to tell other family members to go check them out.