Costco shoppers, be on the lookout for a 4 pack of Conserv Energy CFLs for $0.89 after Instant Rebate. There is a limit of 10 per customer. You may have to look around a bit to find the sign, but they are $4.89 with a $4 Instant Rebate.
There is NO guarantee that every Costco has them, but at this price it is certainly worth a quick look. I found them on an endcap over in the home side of the store.