Couldn't believe I hadn't added this one! OMG, as my students say. Up there with the Ancient History Sourcebook as an online source site (and that's a big call).
An archive of primary sources from the c15th to the late c19th maintained by professors from significant universities in Europe and funded by the UK Arts & Humanities Research Council. Easily searchable.
"The Center for Research Libraries, the University of Chicago Library, and the ARTFL Project, (American and French Research on the Treasury of the French Language) have cooperated on a project to digitize pamphlets and periodicals from the French Revolution of 1848 held by CRL as a test of electronic distribution of archive material via internet.