i agree about daydream nation and goo... i also really like their newest, sonic nurse...but if you're a sonic youth virgin, i would recommend starting with their earlier albums, because that makes the most sense to me when you're starting to get into a band. but yeah, dn and goo. really good.
Sonic Nurse is actually the only album of theirs I do like, which a lot of people who are fans find slightly odd. Nevertheless, it's a beautiful album! That said however, I would say to start with a more critically acclaimed album, like Daydream Nation.