+1
I got an email:

"Dear Warrener:

I hope this finds you well. I wonder if your students have interest in XXX project to help me blahblah...

Sincerely,

Jack"

What does "I hope this finds you well." mean here?

Comments 
At least in American English, it's not a common opener. However, it's meaning is

I hope you are in good health when you receive this letter.

this finds you = this letter comes to you

well = in good health.
Hi,

'I hope that when you receive this email, you are well'.

It's polite and stylish. It also sounds to me slightly old-fashioned, particularly when written in a modern medium like email.

Best wishes, Clive
I think "I hope this finds you well" usually means something like "I hope your health is good and that things in general are OK."
I believe it simply means that this person wishes you're doing well ... that's you're good. Emotion: smile
It's a wonderful and courteous way of saying "i hope you're doing well". 

In this day and age of abbreviations and misspellings, it's unfortunately one of the many rapidly disappearing expressions of the endangered species we refer to as the English language. 
It basically means, I hope you are doing well and that things are going smoothly for you.
(From the book Hope's Journey)

Is the "doing" necessary?