The New York Times Select service ended on September 19, 2007, access to articles (including obituaries, wedding announcements, etc.) will now be free from 1987 forward, as well as everything prior to 1923 (1851-1922) which is in the public domain. Access to the rest of the NY Times archives will still have to be purchased. Articles are normally available as PDF files.
The New York Times is also offering free access through the end of the year to the entire archives to its current Times Select customers. If you’re looking for something that appeared in the New York Times between 1923 and 1987 The New York Times will offer users the option to purchase single articles ($3.95) or 10-article Archive packs ($15.95, good for 30 days) for access to articles published between years 1923-1986.