Open a new Ameritrade account before March 31st and trade commission free for 30 days.  And if your new account is a non-IRA account funded with at least $25,000 Ameritrade will also give you $100.   Commission free trades are limited to 500 equity trades within 30 days of account funding.  Accounts must remain open for nine months.

See:
http://www.tdameritrade.com/offer/special.html