Spartacus

I have heard a little about 'Spartacus' before, but I had never actually used it. However, I have found that it has a number of useful resources.

On the Weimar Republic specifically, there are a few sections:

http://www.spartacus.schoolnet.co.uk/GERweimar.htm

Treaty of Versailles
Spartakist Rising
German Revolution
Bavarian Republic
Ruhr Occupation
Freikorps
Inflation
Unemployment
Dawes Plan
Reparations
Beer Hall Putsch
Kapp Putsch
Treaty of Rapallo
Young Plan
Locarno Treaty
League of Nations

These sections give an overview of the topic, sometimes with relevant diagrams, and links to other areas of interest. Although some areas are brief, it is concise and a good, quick recap.