Amazon offers the GE 6-Outlet Adapter Spaced Wall Tap for $5.31. Clip the 5% off coupon on the product page to drop it to $5.04. (Home Depot charges pennies more via pickup.) With free shipping, that's tied with last week's mention and is the lowest price we could find by $2. It turns two grounded outlets into six outlets.

Note: This may take up to three weeks to ship.