Id-Rack via eBay offers the Xlong 28" x 20-Foot Solar Pool Heater Panel for $84.99. Apply coupon code "P20MEMDAY" and check out via PayPal to drop it to $67.99. With free shipping, that's $11 under our mention from last August and the lowest price we've seen. (It's $64 under the best deal we could find for a similar heater panel.) It converts solar energy into heat, which is piped into your pool water. Deal ends May 29.
Note: This coupon can only be used once per account.