If you REALLY want to get into the wilds, the White Mountain Nat'l Forest is it, esp. the Pemigewasset Wilderness is it--there is even some old-growth forest near Whiteface mountain. There are huts along the Appalachian trail, to which you can ski or hike and spend the night--and they're REALLY basic, but booked up months in advance. If you're into winter camping, just head up 93N to Lincoln, NH, then take your pick of which trailhead you want.
North of Manchester, it starts getting much more moutainous, with fewer heights of land between them, so try Rte 104 to Rte 16N, towared Ossipee. There, the parkland is more tame (flatter), but still pretty wild. Or You keep going on 93 to N.Conway and take Rte. 302, through Crawford Notch and if you tired of say Zealand Notch (See link below) you could head over to Bretton Woods for some 1st class x-c, groomed skiing.
Here's a site with a topo map and much info about one of the most popular sites, Zealand Notch and Falls (I've been there in winter, xc skiing and it IS beautiful!). This site has great descriptions and stunning photos:
Zealand Notch, Zealand Falls, Zealand Ridge and Thoreau Falls via Zealand, Twinway, Zeacliff and Ethan Pond Trails
Here's another site detailing a ski trip through the wilderness, including Pinkham notch, near Mt. Washington (NOT the friendliest xc ski country, but okay for hikers):
A winter mountaineering and nordic backcountry ski excursion to the White Mountains National Forest in New Hampshire.
For a map of the Pemigewasset wilderness and trailheads check out this link (It lists regular campgrounds too, but you can just ignore those!
Yahoo! Maps
Another option is to take Rte 2 West, to Greenfield, then follow it to Charlemont, then down 8A to Hawley state forest or stay on Rte 2 to Savoy state forest. It's PRETTY wild there too--Savoy also has basic huts you can reserve.
You're not going to get anyplace really wild, an hour's drive from Boston, but the extra time is worth it! have fun!