Get It Now From TigerDirect.com
It may not be a lot of memory at today's standards, but it's fast enough (PC6400 DDR2, 800MHz,) produced by reputable Crucial and you can't beat free.

The rebate is handled by Crucial, who's known to honor rebates without problems, and it's valid only one more day.

Originally at $49.99 - $15 instant savings - $35.00 mail-in rebate = $0 but you'll have to pay for shipping.