If you are looking for cheap (low priced) tires:

Pick up whatever is for sale at Nashbar or Performance right now.

Performance has their Forte GT 700 x 25 tire on sale right now for $6.99, plus they have a discount depending on your order size. Not a world class tire, but for $6.99, why not?
http://www.performancebike.com

Nashbar has the Hutchinson Quartz for $9.99, 700 x 23.
http://www.nashbar.com

Niagara Cycle Works has several tires on sale for under $10.
http://www.niagaracycle.com

I have gotten excellent customer service from all three of these vendors.