Capital One is offering a $50 bonus when you open an InterestPlus Online Savings account  using the promotion code BANK223DF with at least $10,000 by January 15th, 2012. Capital One’s online savings bank offers competitive rates compared to other online savings accounts , gives you a 10% quarterly bonus on your interest, and has no fees.
Here is some of the legalese:
You will receive a $50 bonus if you open a Capital One Bank InterestPlus Online Savings (IPOS) account online only, enter the offer code at the time of account opening, and have $10,000 or more on deposit on 1/15/2012. This account must be your first account with Capital One Bank. The deposit will be deposited into your account 4-8 weeks after 1/15/2012 and the account must be open at the time the bonus is credited. The bonus will be reflected on your monthly statement and will be included in your year-to-date interest and year end tax reporting. This offer cannot be combined with any other offers.
I opened one of these accounts under a similar Costco/Capital One promotion  last year and have been happy with it. If you are a Costco member, especially an Executive member, then the Costco promotion is better. With an Executive membership you get $60 in bonus money ($20 for Gold and Business) plus a higher interest rate (0.91% vs 0.80% as of today). Finally, the minimum you need to deposit to get the rate and bonus is $5,000, not $10,000.