Almost all articles in the New York Times are free online, for about a week, and then go behind the pay wall. However, NYT permits readers to generate permanent links to individual articles. Here is a link generator created by Aaron Swartz. Paste the URL of an NYT article into the box, and click "Go". You will see a the URL of the permanent link to the article. You should use this permanent link in your blog posts.

If you know how a bookmarklet works, you can find one at the upper right corner of Swartz's site. Drag the bookmarklet into the Bookmarks toolbars of your browser. Next time when you are reading a NYT article, a single click of the bookmarklet will give you the permanent link.