As a busy NYer, your leisure time's too precious to be so damned leisurely about how you spend it. Type-A your off hours, with TravelSkoot
A flexible, GMap-based travel planner that intricately organizes themed day trips in NY and beyond, Skoot was developed in Englewood, NJ, where the creators apparently had a keen interest in everywhere but Englewood, NJ. Obsessively-commented NY options include everything from One-Track Food (S'mac, Crif Dogs, PB&J), to Punk History (where Dee Dee Ramone wrote "Chinese Rocks", where Sid Vicious died), to Hip Hop History (Queensbridge Houses, Unique Auto Sports), to Gossip Girl Does New York, including hotspots like The Box, Butter, and other places high school girls can get in, but you can't. Skoot also lets you build your own itineraries, which you can use for your own purposes, or for passing off to visiting friends & relatives (e.g., for dad: "Apartments you could have bought me for $50,000 when I asked ten years ago")
As for being walking-around friendly, Skoot'll send any itinerary to your email account or phone -- because the need for leisure's human, but turning off your Blackberry? Madness.