We go through about 5 bottles of seltzer every week in my house.  Although we buy the large bottles and recycle them, it is still a lot of plastic we purchase.
I discovered the seltzer maker by Soda Stream.  Check out their online store which has products starting at $89. 
I am a fan of the Pure machine, with sleek lines that would blend in on the kitchen counter.  It would pay for itself in about 16 weeks.  Plus the carbonators can be refilled, futher reducing waste.

Sodastream Fountain Jet Soda Maker Starter Kit