Update 3/1/08: The promo has been extended. The offer is now good through 3/31/08.
Discover Bank is offering between $20 to $100 for opening an account. The best deal is the $20 bonus since it requires only a $2,500 deposit. The $50 bonus requires a $50,000 deposit, and the $100 bonus requires a $100,000 deposit.
The account must be opened by 2/29/08, and the minimum deposit of new funds must be received at Discover Bank by 4/15/08. The funds must be on deposit for at least 90 days. The bonus will be credited to your Discover Bank account by 4/20/08.
Since the deposit must remain in the account for 90 days, you'll have to be careful that you don't miss out on a higher interest account some place else. For example, if you can get 0.5% higher interest at another account for 90 days, you'll lose $125 in interest for a $100K balance. That's why the $20 bonus could be a better deal. With only a $2.5K balance, you would only lose about $3 in interest.
Discover Bank's Money Market Account has a history of decent rates for large balances. The current rates are a little low compared to other online money market accounts. The yield for a $10K minimum balance is 3.56% APY and the yield for a $50K minimum balance is 3.66% APY.
Discover Bank's Money Market Account has some nice features including limited check writing (first set free), debit/ATM card and the ability to transfer funds between bank accounts using Money HQ via Discover's online Banking Center. I can't find any info about transfer costs or limitations. Also, I can't find any mention of monthly service charges. No interest is earned if the balance falls below $2,500.
Discover Bank is a member FDIC (Certificate # 5649).