More formal:
* Are you aware that...
* Have you heard that...
* It may interest you to know that...
* You might be surprised to learn that...
* Do you realize that...
Informal:
* Guess what...
* You won't believe this...
* This is crazy, but...
* Check this out...
* Did you see that...
Intriguing:
* Did you ever wonder...
* Have you ever considered...
* This might blow your mind...
The best alternative will depend on your audience and the tone you want to convey.