SuperGoodDeals offers this
8GB MicroSD Card for $5.99. Coupon code "DealNewsVIP1" cuts that to
$4.99. With
free shipping, that's the lowest price we could find for such a card that's shipped from the U.S. by a buck. It includes a case.
Don't need it soon? Powerstarforever via eBay offers an
8GB MicroSD card with an Adapter for about $3.45 with free shipping. (It's priced in Canadian and the exchange rate may vary.) However, it ships from Hong Kong and may take two to four weeks to arrive.