I recently attended a workshop at the New York Cultural Center - Home of the New York Archives, Library and Museum. Many different on-line and on-site resources were presented. If you ever need to do research on something related to New York (or any number of other things) these ladies and gentlemen will definitely be more than a little helpful.
New York State Archives - Images, Audio and Video Page
New York State Library - Main Page
New York State History Blog
Preliminary Emancipation Proclamation resources
Selected Historical Documents from the library collection
Significantly large array of documents from the Revolutionary and Civil Wars; as well as Native American and other cultural stuff. Great resources for preparing lessons.
Each link (and there's a LOT of them) links to vetted sites of sources from outside the NYSED resources.
Old Fulton New York Post Cards
Odd name, amazing results. It's not what it sounds or looks like. This site has literally MILLIONS of pages of old newspapers scanned and OCR cataloged for search-ability. Go ahead... click on it, suggest a term and be amazed.
New Netherland Institute
All about the earliest days of New York - before it was New York.
Factory Investigating Commission files
Files from the NYS commission established after the 1911 Triangle Shirtwaist Fire.
New York Lantern Slide Collection
This is a collection of several thousand "lantern slides" prepared by the New York State Education Department. These large format slides were send out to local schools for use as visual resources. Thousands of images of "stuff" from around the world. Perfect resources for all different kinds of social studies, ELA and science classes.
"A comprehensive, categorized & cross-referenced list of links that point you to genealogical research sites online." (Quoted from the site.)
Going back to the 1930s. If you're a teacher, this thing will suck you in for a long long time. Think of it as a test bank on steroids. Enjoy!
On-Line databases available to any New Yorker with a New York State Library Card.
What's that? You don't have a NYS Library Card? Not to worry! If you're a resident, you can get a card! Go here for directions: http://www.nysl.nysed.gov/apply.htm
I know many schools have databases available for teachers and students, but this database is available to any New Yorker anywhere - you don't have to be at a school.
Joseph Smith Papers
Collection of images and transcriptions of the written words of the founder of the Church of Jesus Christ and Latter-Day Saints (Mormons)