BuyDig offers the SanDisk 16GB Extreme Pro CompactFlash Card
(pictured), model no. SDCFXP016GA91, for
with free shipping. That's $4.69/GB and the lowest total price we could find by $10, although we saw it for $15 less in November. It features read and write speeds up to 90MB/sec.
Update: The price has since fallen to $72 with free shipping ($4.50/GB).