This may be targeted, but Delta just sent me an email with a 50% promotion when you buy miles from December 1- December 30, 2010, with a maximum purchase of 60,000 miles. Link. I can’t guarantee it’ll work for you, but if you need to top up an award, it may be worth it to buy through this link in case you get the bonus, which should post within 24 hours.
Generally buying miles doesn’t make sense, unless you are looking to use them for premium class travel. For example, with this promotion, I could buy 90,000 miles for $1,680. 90k miles is two first class domestic tickets (including Canada). For 100,000 you can get a business class ticket to Europe, which usually go for $3,000 and up.
FYI Delta Skymiles are one of the most inflated frequent flyer currencies, so don’t expect to redeem them at “low” levels very easily. Lucky for you, if you need help booking a Delta award, you can enlist my professional services. I am an expert at finding low level awards- even when Delta phone reps say they aren’t available.