Try White Brite Laundry Whitener for free with online rebate. I love this online rebate, no postage, no envelopes, no copies to be made. Just print a confirmation page.
Anyway here are the details. I found a hang tag on White Brite that says Try Me and Save up to $4 off. It also says "valid only on the purchase of specially marked product" and "offer expires 6/30".
HOWEVER, I went to the website www.mypromoinfo.com/whitebrite and was still able to submit my request even though it is 7/4. As for the specially marked products, having a hang tag would be preferable but it looks like it may work without one because the promo code, WB0001, is listed on the site and the redemption code (a date and time stamp) is printed on each bottle.
I found mine at Walmart but could be available elsewhere. If you try it let us know how the deal worked out for you.