By way of personal experience, word of mouth, incessant research on Google, and some reference to all of the sites linked to here, I've compiled a guide for my fellow urban car-less skiiers and snowboarders out there who need their fix of snow this season but may not know the best way to get to the slopes.
There are a large variety of companies that provide buses from NYC locations, typically by 6 or 7am, for travel to New York area ski resorts, or as early as 3 or 4am for travel to Vermont resorts. Expect your bus to leave the slopes at any resort by 4pm to head back to the city. Cost may range from $60-120, depending on whether you are traveling mid-week or weekend and whether or not you have your own equipment, and will cost more if you need a lesson (although be sure to check out beginner packages that cost less and include a lesson, but restrict you to "beginner" lifts/runs). While some of these groups may focus on singles and/or young professionals, many offer mixed crowds.
Some downsides: you may be forced to watch The Ali G Show on the bus's DVD system, your fellow skiiers may be very, very loud and drinking, and you may/will get hit on. Also, many of these buses arrive at exactly the same time to your chosen mountain, so be prepared to wait awhile for your rentals and expect long lines at the lifts on weekends (on a recent Urban Sherpa trip, I boarded a 6am Saturday bus to Windham and did not ski my first run until nearly 11:30am). The upside: make new friends/find skiing and boarding companions, you don't have to drive, and you can sleep on the bus, as long as you're not getting hit on.
Try These For Day Trips:
Adirondack Trailways Bus has day trips to Belleayre Mountain. (As, let's call it an advanced beginner, I'm a big fan of this mountain!)
Blades NYC takes New Yorkers to Hunter, Windham, Mount Snow (VT) and Camelback (PA) Mountains. Through March 20, you can find a day trip to at least one of these mountains operating nearly every day of the week/weekend from Blades, with the exception of a few Mondays. Breakfast is provided on the bus.
Emilio's Ski and Snowboard Shop in Forest Hills runs day trips to Okemo (VT) on Saturdays and Holidays; Hunter Mountain on Tuesdays, Thursdays, Saturdays and Sundays; Mount Snow on Sundays; Windham on Wednesdays and Holidays; and also sometimes has day trips to Stratton (VT). There is always a pickup at the Forest Hills shop, but most trips also offer at least one Manahttan location as well, and some also have Brooklyn stops.
Homage Brooklyn runs day trips to Hunter every Tuesday through Thursday and weekends, and also has trips to Stratton, Okemo, and Mount Snow. Pickup locations are in Manhattan and Brooklyn. This seems to be one of the "cheaper" options... Weekend bus to Hunter, for example, is only $69, including lift ticket, but not including rentals.
NJ Transit operates a bus to Mountain Creek on weekends and holidays.
Outdoor Bound runs a lot of cool day trips like snowshoeing in the winter, and hiking in the summer, and once in a while you'll find a skiing day trip on their calendar (such as Singles Skiing on Sunday, February 13). (Also check this group out if you've ever wanted to climb Mount Kilamanjaro...).
Paragon Sports in Manhattan is known for running ski and snowboard trips to Hunter and Windham Mountains, and serves a "light breakfast" on their buses, but since no trips are listed on their site, I have to assume there are no upcoming dates.
Urban Sherpa Travel will take you by bus most weekends, and some weekdays, to Hunter or Windham, and sometimes also sponsors both day and overnight bus trips to Killington (VT) and Stratton.
Another resource you may not have thought of is Meetup. I won't post all of the different meetup groups that run skiing and snowboarding trips, because it seems infinite. Just go to the site and type in keyword "skiing" and you'll see what I mean (make sure to scroll down to the list of groups).
Want more than just a day trip?
The Ski & Snowboard Club of New York has two more upcoming weekend trips this ski season from NYC, the first heading to Stowe, VT, from Friday, February 18 to Monday, February 21 (President's Weekend), and the second to Lake Placid, NY, from March 4 to 6.
Dyamic Outdoors is also hosting a weekend ski trip, from NYC to Killington, March 4 to March 6.
Being the exceptionally snowy ski season that it is, I am not the first to come up with the idea to disseminate the above information, so here are some more articles you can follow up with :
Glenwood NYC Rental Management Company's List of Skiing and Snowboarding Daytrips
New York Magazine Article: "Top 5 Quickie Ski Trips"
Time Out New York Article on Ski Resorts 2-5 Hrs from NYC
I have yet to find any bus that goes directly to Plattekill mountain upstate... If you know of one, please leave a comment.
UPDATE: Tried the Homage bus to Hunter Mountain and had a really great time. Bus was right on time, even left early, and got us to the mountain with plenty of time to ski. I also liked the skiing options better at Hunter than Windham, and the rental process was a lot smoother and quicker, as was the rental return process. I probably will avoid Windham in the future and go to Hunter.