Part 2: Where do I go?
So you have skate skis, one way or another, or maybe you're going to rent some. Where should you go?
The most common option around Boston is Weston. They have snowmaking, night skiing, Tuesday night races, and almost zero interesting terrain. They're the only place you can regularly ski midweek if you work in Boston and have a day job. If you're looking for the simplest exposure to nordic skiing, go to Weston, rent skis, duff around for a bit. Done.
But you might not like it that much. Skiing at Weston is like racing at Wells Ave, or mountain biking around the Fells -- nothing special, but it's close and convenient. Since you're a cyclist, your other option was probably riding the trainer in your basement, so maybe you can't even tell that the scenery and terrain variety at Weston sucks.
Assuming you'd like to make an actual experience of it, and say, go down hills, ski through the woods, or see natural snow, you're gonna need to get in the car. There's a surprising number of choices to ski in New England, so it's a tougher choice than you might think. How long do you want to drive and how much snow is around?
Great Brook (30 mins) or Windblown (1 hour), both of which are natural-snow-only places, with real trails, that can be a half-day trip. Windblown is currently in the process of changing hands from a family that has run it for a million years, to a group of hardcore Boston skiers who have a "master plan" for improving it. In a few years it may be a totally different place, although any change will undoubtedly be for the better.
If you've got an entire day to spend out on the trail, there's good skiing at Waterville Valley, Gunstock, Pineland, and probably a bunch of others I'm forgetting (looking forward to some comments, here!) that are 2 hours or so from Boston on major highways. These have bigger trail systems and more snow than Great Brook/Windblown.
If you're making a weekend of it, well, that pretty much opens up all of New England to you. I can't possibly enumerate all the options, but I'll list a few favorites:
Great Glen Trails
It should be noted that all of these exist in the vicinity of major alpine ski areas, so even if you don't want to nordic ski for two days they can be bundled into an incredible, average-cyclist-crippling, winter weekend.
If your plan all along was to go only to Weston you probably found this pretty useless. Just wait until tomorrow, we'll talk about technique, and how you don't have it!
Update! Toby found a map of every ski center in New England.