I went on a little tour of Long Island this summer - would love to give you some recommendations!
My favorite: Pellegrini Vineyards. Lovely place with great wine. The wine tasting flights are not too expensive at all and allow you a broad choice of many of their wines. If you're going with a couple people I would definitely advise that one of you gets the more expensive flight that allows you to try some of their more expensive stuff - a lovely signature red blend with more age on it that you can compare with the younger vintage and their ice wine. If you're a fan of gewurztraminer I'd recommend that as well. In the tasting room you can fill up your flight tray (which has labeled spots for each wine) and bring it outside to sit overlooking the vineyard (although it may be a bit colder than when I went over the summer).
2nd place: Lenz winery. The people there are super nice and the wine is great - we took our glasses outside each round of the flight and sat in the garden to drink. Also fairly reasonably priced. We got there like right as they were supposed to be closing but they welcomed us anyway. I believe I really enjoyed their merlot - and I would recommend getting a merlot pretty much everywhere you go as I think long island does a great take on it, though lighter bodied than you'd find elsewhere it tends to have a little touch of barnyard/horse blanket that I personally really enjoy.
Macari Vineyards: The wine was nice, as was the view. Nothing super notable and the tasting is fairly rigid without much choice, but a fine stop along the way. I visited there because they bought out Galluccio Family winery a number of years back which used to be Gristina Vineyard (sold for the record high price for a LI vineyard at the time). Gristina had gotten many accolades and great scores before being bought and were especially renowned for the parcel of land they deemed "Andy's Field," which even got some mentions in the NY Times:
http://www.nytimes.com/1999/04/18/nyreg ... -andy.html http://www.nytimes.com/1998/11/01/nyreg ... vines.html . Unfortunately, when I asked the woman serving the wine about it (who honestly didn't seem to have much of a clue about wine) she conveyed that they don't do any wines from particular plots, which I found kind of sad, given the reputation of Andy's Field under Gristina.
Osprey's Dominion: The wines here were pretty good and the place is lovely - they're got picnic tables and a giant turbine and it's quite picturesque out in the vines. The guy serving the flight, on the other hand, was kind of a dick. He was clearly not very happy with what he was doing and sullied the mood a bit for us. When we asked for our last wine to be the cellar selection of the month or whatever they call it he was kind of like "yeah I don't know if we're really doing that this month" or "I think we're out of the one we were doing this month" or something. Though then the young guy working with him jumped in, pulled a bottle of their reserve cab franc off the shelves and said "well let's just say this is it, then." He started up a conversation with us and really saved it for them after the mood of the other guy. The flights, as I recall, were also not the cheapest, although they've got little cracker pillows there at the bar which make for great palate cleansers between wines. The cab francs are good - the reserve was quite nice and elegant - and the cab sauv (which they advertise as high scoring) was pretty good, too.
Bedell Cellars: Disappointing and doesn't live up to the hype I've read. Flights a little too pricey as well, and they don't give you any flexibility whatsoever - both flights we tried force the rose on you. The gewurz is quite disappointing, even though it's supposedly award winning or something. The flights don't allow you to even try their best wines - you'd have to buy a glass or bottle for that, which they even mark up over retail a fair bit. Would not recommend going here - if you want to try their best wines (i.e. the Musee) it'd be better to just pick up a bottle at a local wine store.
Not wine, but food! North Fork Table and Inn: Incredible place, right near all five wineries listed above (they're all within like 8 mins of each other by car and this is like 5 or so from the one farthest east). Small place with a great menu, very fresh local ingredients and you can do a wine pairing with the meal (if you haven't had enough already

). Reservations are hard to get, but you can make them up to a month in advance online:
http://www.nofoti.com/ Let me know where you end up tasting and how it goes (especially if you visit somewhere else that's not listed above)!
Hope you enjoy!