There actually are better TD Ameritrade offers out there. I just signed for 20000 Starpoints (which I can transfer into 25000 AA miles) for just a $25000 deposit into a TD Ameritrade account.

And Freefrequentflyermiles.com has a long list of their offers - all of which have been extended to Sept. 30. According to my research on FT, TD Ameritrade has been offering these deals consistently since 2003!

There are a number of TD Ameritrade threads on FT. I'm not sure which is the best.

Here is what Freefrequentflyermiles.com lists for TD Ameritrade's offers (again all have been extended to Sept. 30):

# American (Expires June 30, 2010.)
Initial Deposit Miles earned
$2,500 5,000
$10,000 15,000
$50,000 25,000

# Delta (Expires June 30, 2010.)
Initial Deposit Miles earned
$2,500 5,000
$10,000 15,000
$50,000 25,000

# United (Expires June 30, 2010.)
Initial Deposit Miles earned
$2,500 5,000
$10,000 15,000
$50,000 25,000

# Continental (Expires June 30, 2010.)
Initial Deposit Miles earned
$2,500 5,000
$10,000 15,000
$50,000 25,000

# U.S. Airways (Expires June 30, 2010.)
Initial Deposit Miles earned
$2,500 5,000
$10,000 15,000
$50,000 25,000

# Starwood (Expires June 30, 2010.)

Initial Deposit Points earned
$2,000 3,000
$10,000 10,000
$25,000 20,000
Note:

* Since 20,000 Starwood points gets you 25,000 miles on a large number of airlines (except United or Continental), the $25,000 Starwood offer is by far the best for initial deposits of $25,000 or more.

# Amtrak (Expires June 30, 2010.)
Initial Deposit Points earned
$2,500 5,000
$10,000 15,000
$50,000 25,000