Ceska Posta
Website of the Czech national postal service.
http://www.cpost.cz/

CzechSite Travel Guide
Contains information and advice on the Czech postal system, as well as a post code search engine.
http://www.czechsite.com/communication.html

In Your Pocket
Contains brief notes on the city's main post office and local postal rates.
http://www.inyourpocket.com/cr/prague/en/category?cid=3175&chid=400

Prague Tourist.com
Offers basic advice on sending a letter or package from Prague.
http://www.praguetourist.com/tourist/vpravo2.htm