UPDATE - 4/10/2012
Pretty different scenario currently - see this post for the summary:
http://www.flyertalk.com/forum/16588684-post929.html
UPDATE - 7/21/2011
I've basically re-written this post to reflect the current status of offers from Fidelity.
There are two types of offers at the moment: Offers for new customers only (the definition of "new customer" is a bit tricky and there is lots of info about that in this thread) and offers for existing customers adding new funds. Much has been written in this thread about ways to get multiple bonuses. I'll stay out of that in this post and just give the links to the current offers:
New Customers:
AA:
https://scs.fidelity.com/other/offer...shtml?MSC=AA01
United:
https://scs.fidelity.com/other/offer...shtml?MSC=UA01
New or Existing Customers:
Delta:
https://scs.fidelity.com/other/offer...on_delta.shtml
American Express Membership Rewards:
https://scs.fidelity.com/other/offer...nexpress.shtml
All are for 50,000 points/miles. Clearly, it pays to be careful where you use your "new" status if you have no Fidelity account.
In the year since I originally posted, it seems that the Delta and now the Amex MR offers have become available to
existing account holders. That means you can actually get a few of these deals, if you do it carefully.
The best info that summarizes the steps is
HikerT's post here:
http://www.flyertalk.com/forum/16588684-post929.html
Currently, the Amex MR info is still in flux.
NOTES 12/31/11:
I believe the Amex MR is fully over.
I have started a TD Ameritrade thread to keep that related, but different, discussion out of this thread:
http://www.flyertalk.com/forum/miles...us-thread.html
NOTE 3/5/12:
As I don't pay a ton of attention to this thread at this point, please send me a PM if there's a significant reason to update this initial post.