the ink pad is wonderful - it's teeny, but they have it completely packed with stuff. it's on the west side of 8th avenue, near the 12th street corner (between 12th/13th). a little pricey, but very cozy. the website is
http://theinkpadnyc.com/. it's the only true stamp store in the city.
kate's paperie is fantastic with multiple locations. extremely pricey, but the papers are gorgeous. there's not a whole lot of stamping stuff, but their scrapbooking section is growing.
another place you might try is paper presentation on 23 West 18th (i think between 5th & 6th).
http://paperpresentation.com/ again, not a whole lot of stamps, but they have lots of embellishments and papers.
lee's art store on 57th between 6th and 7th is more of a true art store, than a crafts store, but they do have some crafting supplies. they have a small stamp section, and their scrapbooking section seems to be growing too.
pearl paint in chinatown at canal street also has crafting supplies. their prices are supposed to be good, but i hate the area because it is always packed and insane. (but if you're interested in some knockoff designer bags, it might be worth it)
if you're willing to go out of manhattan, you can try craftique in brooklyn. i hear they have tons of stuff for scrapbooking !! i've never been, but their number is 718.854.0835 and address is 4401 17th avenue.
of course, there are michael's and joann's and ac moore's outside of the city, but it's probably not worth going since you probably have those in your own neighborhood. i also hear there are more scrapbooking/stamping stores in long island, but am not familiar with any of them.
enjoy your time here!
caroline