More and more universities are establishing digital collections of historical papers, many of which contain important clues for genealogists. The New Hampshire History Bookshelf is another example that includes two collections: New Hampshire History and New Hampshire State Documents. You can search the collection and view the images for free. As an example, I searched for an ancestor that I knew lived in New Hampshire at the time of the revolutionary war. The results included a document that showing he served under General John Stark. Only a few years ago I would have had to travel to Concord or Washington D.C. to view these documents. Have fun with this collection, especially if your ancestor lived in New Hampshire.
Here's the link:
The New Hampshire History Bookshelf