Formal:
* Are you aware of...?
* Have you been informed about...?
* Have you received information regarding...?
* Is this news to you?
Informal:
* Did you catch that?
* Did you hear about...?
* Did you know...?
* Have you heard the news?
* Guess what?
* You wouldn't believe this...
More specific, depending on the context:
* Have you seen...? (If it's something visual)
* Have you heard about [specific event/topic]? (If you're referring to a specific event)
The best phrase to use will depend on the context and the level of formality you want to achieve.