When I visited Prague in the late 1990s I went to Libri Prohibiti, which housed collections of samizdat literature and other materials. There I stumbled across a dusty folder containing five leaflets that had been handed out during the 1968 invasion of Czechoslovakia. One of the archivists generously let me use their photocopier to make copies.
Some of these leaflets look like they were targeted at the invading troops; others seem aimed at boosting morale of the citizenry and encouraging continued resistance.
Using the links below you can download PDFs of the original flyers and see the English translations. (The last leaflet was double-sided.)