Here is a signup bonus for Mileage Plus Dining (different from the one posted above by pgary):
Subject of email is "Premier members: Earn 2,000 bonus award miles plus VIP status with this exclusive offer"
"Terms and conditions:
"This bonus offer is open to all United® MileagePlus® Premier® members who join MileagePlus DiningSM and do not currently have a dining profile. To qualify, you must join through the registration on this page and create a dining profile, including creating a web login, and remain opted in to receive emails from MileagePlus Dining with a valid, deliverable email address. You must also continue to satisfy other Online/VIP level criteria to earn this bonus.
"To earn this bonus, you must first join MileagePlus Dining through the link on this page by July 1, 2015. Within 30 days of joining MileagePlus Dining, you must dine at any participating restaurant, bar, or club and spend at least $30 (including tax and tip) on your check. Within 30 days of any visit, you must also complete a post-dine survey of the restaurant, bar, or club.
"Please note that all checks must be paid for with a credit or debit card registered with MileagePlus Dining at the time of the visit. You may only earn this bonus once for a maximum amount of 2,000 MileagePlus® bonus award miles. Offer may not be combinable with other MileagePlus Dining bonuses and each qualifying visit can only apply toward a single bonus, as determined by MileagePlus Dining. All account inquiries related to this bonus must be received by October 1, 2015."
(I see a similar MileagePlus bonus is discussed in another thread.)