I had a pitch meeting yesterday with a production company and got some interest in my project. Here is my question. Is it customary to send a thank you note after a pitch like it is with job interviews? I appreciate any and all insight.

-Felipe

If their "interest" means you're forwarding content, then it's a moot point.
No need for thanks if there's material to forward...

However, if no such request happened...
Then try to end the meeting with establishing an open invitation to send more material.

Even if the company doesn't want to buy that particular pitch...
Request to send loglines/synops their way in the future.

They'll likely say yes anyway, even if they're not super interested.
Cuz no one wants to be the guy that passes on the next big thing.

E.D.