Most countries, nowadays, in Biz-Class hotels will have either a telephone and/or a wall-socket that is the "USA-style RJ11" that you find on virtually all modems & laptop computers with built-in modems.

However, there are still a number of countries where you'll have to have an adapter:  - this file has been updated to 2005 (first quarter) and though 'some' of these items are now 'passe' - there is / are still some 'fairly strange'
telephone connectors in some hotels and offices...

Australia has a very strange looking thing that is almost impossible to find outside the country  - it's four square plug pieces with metal pieces on either side,  there are several variations.  However, most hotels will have a phone with an rj-11.  If you're going to spend an extended time travelling in non-major cities, you'll want to buy an adapter at an Australian shop.

Canada: same as USA - rj11 is virtually universally the standard

China: - similar to Australia - but most hotels will have rj11

France: - some hotels have rj11 - but not a lot - remember the French are fairly arrogant in their approach to the rest of the world.  -their standard connector looks something vaguely like this:

   contacts     |---|   (approximately full size)
  --------------|   |
 |                  |  <= cord here or rj11 female socket
  --------------|   |
   contacts     |___|       or click here for jpeg picture file

and you can buy adapters to rj11

Hong Kong:- some hold-over with the BTC (British Telecomm) connectors, but a movement towards the rj11 standard.  The BTC is similar in design to the RJ11 - but it is "flatter" rather than the square-looking format of the rj11.

India: hotels are primarily rj11 - but you find the odd hold-out - the hotel will almost always loan you an adapter

Poland: - strange stuff - but hotels are primarily rj11

Russia: strangely enough I don't remember - probably didn't dial-up?

Singapore: - almost universally rj11 in offices & hotels - some minor BTC in homes

Switzerland: - again - a very strange looking thing - especially in lower-class hotels - jpeg comming soon

UK (United Kingdom (England)):   BTC standard (similar to rj11 but a 'flat' shape, - definately not compatible, but adapters are quite easy to find in airports, variety & other shops

USA: - universally rj11