Mainly from the UK, and from the last 100 years. Search by person depicted (e.g., Thatcher, Gorbachev, Thatcher and Gorbachev); by year (e.g., Hitler and Stalin in 1941 or 1942), by design elements (e.g., cartoons referencing sculpture by Rodin, or cartoons with zebras), by topic (e.g., BSE, Falklands War), by artist (e.g., William Hogarth, L.G. Illingworth, Carl Giles, Steve Bell) or by publication outlet (e.g., Punch, Evening Standard (over 10,000 from Evening Standard alone). There is a handy searching wizard as well.
http://opal.ukc.ac.uk/cartoonx-cgi/ccc.py