i have been cleaning out my spare parts closet recently, and i have come across 3 modems that i was going to put up on ebay or craiglist. you can have first stab at them if you want...paypal would be the best way if you are interested.
1. motorola sb4100 - $10
2. motorola sb5100 - $25
3. motorola sb5120 - $30
plus shipping...another $5-10.
EDIT:// crap...these are cable modems...sorry just realized you need a DSL one