Primary Sources in History
The National Parks system has made available a number of really fine primary sources. If you are interested in the History of the National Park Service or some of the National Parks, check this out.
For those interested in Victorian London, there is an entire site devoted to primary sources here. I really like first-hand accounts rather than much of the modern trend of historical revisionism. I like to know what people at the time thought and said about the events they experienced.