What's your range within NY? Do you hike at all? If you hike, one of my favorite fall hikes is the loop at Sam's Point Preserve. It has a lot of bang for your buck - the ice caves, a waterfall, brilliant red bushes in fall, a nice patch of birch trees with fall color, views from High Point, etc. I have a gallery posted from a fall hike two years ago:
Sam's Point
Some of my other favorite walks and hikes are Breakneck Ridge (Hudson Highlands), Vanderbilt Mansion (Hyde Park, easy), Ferncliff Firetower (Rhinebeck, easy); Sage's Ravine, Race Mtn, Brace Mtn, Bash Bish Falls in the Taconics; Wittenburg, Twin, Indian Head, Kaaterskill Falls, Ashokan Reservoir in the Catskills; Gertrude's Nose in Minnewaska.