The Centre for the Study of Ancient Documents, run out of Oxford. Seems to have an eclectic assortment of images of primary sources and translations from many Classical and early Medieval civilisations.
You'll need to be able to read German and Classical Latin, but once those minor hurdles are overcome this is a rich collection of primary sources on early German history. I only had a brief peek but it seems to focus on ancient & medieval Germany. I guess they're written in Latin as it was the lingua franca of Europe at the time. They're organised into books with chapters and indices so it's unlikely they were written in Roman times (or at least it seems so to me).
Actually, the MGH is a collection of sources mainly for medieval Germany (of course including areas that are not German today), initially started with the intent to create a complete edited version of sources for the middle ages. They are in fact organised by type, like legal documents, letters, chronicles, etc., whereas chronicles are also organised by author.
It's an invaluable reference for everyone doing work in medieval history. By the way, the link you saved doesn't work, I'd instead use this one: http://www.mgh.de/dmgh/
A group of digital collections focussing mainly on audio recordings from the C20th, medieval manuscripts & images, pamphlets & drawings, photos and songs from World War II.
This is a guide to creating lessons using primary sources provided by the Library of Congress. They've just started a new initiative helping teachers use primary sources in the classroom; I went to the site they're set up but there wasn't much there. Maybe it will grow in time.
A series of links to Chinese history collections, provided by the National Library of China. There are a few dead links and the Chinglish can be amusing, but seems as though there are some useful sources in there for Chinese history.
"Mr. Lincoln's Virtual Library highlights two collections at the Library of Congress that illuminate the life of Abraham Lincoln (1809-1865), the sixteenth president of the United States. The Abraham Lincoln Papers housed in the Manuscript Division contain approximately 20,000 items including correspondence and papers accumulated primarily during Lincoln's presidency." Awesome.
This will only excite other Latinists out there. A very extensive collection of Latin sources from most regions in Europe. Bibliotheca Augustana multa bona magistris Latinae est!
The English Emblem Book Project of the Penn State University Libraries in Pennsylvania, USA, has digitized older form of texts, the emblem books, for the 16th to the 19th centuries.
"An emblem book is a collection of images with adjoining text. In an emblem there is a dialog or tension between image and word. Emblems are frequently allegorical in theme. Emblem books are a form of text not altogether familiar to us today. An emblem book represents a particular kind of reading. Unlike today, the eye is not intended to move rapidly from page to page. The emblem is meant to arrest the sense, to lead into the text, to the richness of its associations. An emblem is something like a riddle, a "hieroglyph" in the Renaissance vocabulary -- what many readers considered to be a form of natural language."