I found this article to be pretty good:

http://www.nomadicmatt.com/travel-tips/travel-hacking-guide/

Whether you love Delta, fly United and the Star Alliance, live and breathe Jetblue, or are hooked on Oneworld, all U.S. carriers have a branded travel credit card that gives you 25,000-30,000 points when you sign up and make one purchase.

Above used to be true that you got the points with one purchase but for most no longer true. They now require you to make some dollar amount of purchases like $1000 in first three months to get the mileage bonus.

Chase sapphire preferred gives you 40 k miles but you must spend $3000 in first three months.

Still credit cards are a great way to get a lot of miles quickly. You just need to time your purchases to meet the min dollar purchase requirements.