If the glass is tumbled, it makes a beautiful mulch for a small accent area of for a focal point. It is very expensive to buy bagged tumbled glass so if someone is giving it away, I would take it!
When installing it, use a landscape fabric so that the glass does not become buried in the soil after watering.
I used colored, tumbled glass in a school "literacy garden" that I designed as well as for some clients (I'm a landscape designer) and for some TV garden makeovers I've done.
Glass
also works well in a fire pit and in outdoor fireplaces.
Take a look at the different ways I've used tumbled glass in landscape:
Mulch 101: The Art of Selecting Mulch For Your Garden
And the children's garden:
Create a Memorable School Garden For Your Kids
Shirley Bovshow
"EdenMaker"