Anyone know of a shared shuttle from Long Island (Ny) to JFK?

Not sure about that.. best bet and cheapest way is to jump on any LIRR train to Jamica then hop on the Airtrain.

Here's the page for JFK transportation.

http://www.panynj.gov/aviation/jgtsfram.htm

It lists a "classic airport shuttle" (scroll down to the bottom where it says Long Island).

Depending on where on LI you're starting, the Hampton Jitney makes an "airport connection" stop in Queens from which you can arrange a car service pick up to JFK. In addition to the Hamptons, they make stops in Manorville and also somewhere near Islip.

hamptonjitney.com

I fly from Kennedy frequently to visit family on LI. The LIRR to Jamaica Station, followed by a 10 minute Air Train ride is a great way to get to the airport - unless you have a ton of luggage. There are also a lot of shuttles but, depending on the time of day and how many stops they make, it could take longer than the train.

There are shared shuttles from many of the major towns. If you just look in the yellow pages for the town you will be visiting you should find info.

The train may or may not be an option dependng on how much luggage you have and where on LI you will be going - since some areas have no or dismal train

In any case - if you plan on spendng any time on LI - except visiting people who will lend you a car - you really must have one to get around - so why not rent at the airport?