With the threat of Influenza A(H1N1) or "swine flu," many travel regulations are being introduced across the world that air travelers need to be aware of. The International Air Transport Association (IATA) provides some useful information through their Travel Center web page.
In their Latest Travel Document News, IATA notes:
Travel regulations introduced by Japan, Singapore, Argentina, Belize, Brazil, Colombia, Ecuador, France, Italy, Japan, Panama, Spain, Sri Lanka, Turkey, Armenia, Montenegro & Syria.
They provide links by country for more information, and in addition IATA has made available a Frequently asked questions – Influenza A(H1N1) and Air Travel page that relates World Health Organization guidelines for air travelers.