In Delta SkyMiles members' email boxes this week comes an offer to earn up to 25,000 bonus SkyMiles for utilizing some of the many partnerships the airline has. You can earn these miles without ever taking a flight!Here's how it works: Register first. Then, do business with four SkyMiles partners (such as car rentals, hotel stays, ordering flowers) and earn 4,000 bonus miles. Use six partners, earn 6,000 miles, and so on - up to 25 partners to earn 25,000 miles. Qualifying partner activities must occur between April 22 and June 22, 2009. Be sure to read the full (and lengthy) terms and conditions.