Most countries are member of the International Civil Aviation Organization (ICAO) and as such have signed the " and read about it in Special Airworthiness Information Bulletin CE-10-08.
Language Proficiency Endorsement
As of March 2008 any pilot with a PPL license or higher is required by ICAO to obtain Language Proficiency Endorsement with his Radio Telephony license. This is to make sure that the level of English used by pilots on the radio is of a required standard. All pilots with an RT license obtained before March 2008 will get a LPE level 4 automatically when they renew their license and this LPE-4 is valid for 3 years. A LPE-5 is valid for six years and a LPE level 6 is a lifetime endorsement and needs no renewal. Read ICAO Doc 9835/AN453 (149 pages, 1 Mb) for more info.
ELT, Emergency Locator Beacon
As of its mandatory by ICAO to carry an Emergency Locator Transmitter (ELT) operating on 406 MHz on all International GA flights. The old ELTs (121, 5 and 243 MHz) will not be monitored anymore by CORPAS/SARSAT satellites as of Feb, 1st 2009.
Transport Canada has decided to mandate the new ELTs for most aircraft flying in Canadian airspace, private and foreign aircraft too. Make sure to comply when the rules goes into effect somewhere summer (2010), read more about that in the Canada Gazette Part II.
If you are flying a vintage aircraft, experimental or not, you must take note that the US-FAA has published AC 23-27 which details guidance to both owner and or restorers and FAA aviation safety inspectors when collecting information needed for an FAA approval. This is necessary when parts or materials used in the original construction of the type-certificated airplane are no longer available, or newer, more appropriate materials are now common and would be more appropriate to be used when repairing or replacing components. Read all about it in FAA AC 23-27 Vintage Aircraft.