Newegg offers the G-Technology 500GB G-Connect Wireless External Hard Drive, model no. 0G02148, for $44.99. Apply coupon code "VCO" and use Visa Checkout to cut it to $40.49. With free shipping, that's the lowest total price we could find by $15, although we saw it for a buck less in June. This hard drive can stream media via 802.11n to four wireless devices at once; it also features USB 2.0 and Ethernet. Deal ends August 25.
Note that the above Visa Checkout discount can only be used once per account.