Via Flyertalk, there’s now a promo available for the Capital One Venture^SM Rewards Card that offers 50,000 bonus miles after you spend $3,000 within the first 3 months. That’s up from the 20,000 bonus miles after spending $2,000 that the card typically offers. 50,000 bonus miles can be redeemed for $500 towards travel.

Venture Rewards Benefits
The Venture Rewards card earns “double points” on all purchases. Points are worth a penny per point when they are redeemed towards travel, which is by far the best value among the redemption options. So in effect, the card effectively is a 2% rebate card on all purchases, assuming you always use your miles towards travel.

Other features include:

• No limit to the number of miles you can earn
• No expiration date on your miles
• Use your miles to book any flight you want with no blackout dates
• No foreign exchange fees

The Competition: Barclaycard Arrival World MasterCard
As a card that offers double miles on all purchases, the Venture Card is very comparable to Barclaycard Arrival World MasterCard.

Both cards allow you to use your miles towards travel expenses made within the past 90 days, without any caps on earning or redeeming miles and no foreign exchange fees. One distinct advantage of the Barclaycard Arrival World MasterCard is that it also offers a 10% bonus whenever you redeem your miles for travel, making it essentially a 2.2% rebate on all purchases vs the 2% rebate for the Venture Card.

The signup bonuses are comparable as well. While this Venture card promo offers $500 towards travel after spending $3,000 in 90 days, the Barclaycard Arrival offers $400 towards travel after spending $3,000 in 90 days. The Venture Card has an annual fee of $59, waived for the first year, while the Arrival Card has a $89 annual fee, also waived for the first year. If you spend at least $15,000/year, however, the extra 10% bonus offered on the Arrival card will offset the difference in annual fees.

Update 1/10/14: The Cap One 50,000 point offer is no longer available.

The Barclaycard Arrival World MasterCard offer, however, is still available and can be found at the following link:
Barclaycard Arrival World MasterCard