For those who travel the world a lot and don't have endlessly deep pockets, finding ways to economize spending for international calls and getting Internet access on the move is essential. Over the years I learnt a lot of tricks and at some point started the Prepaid Wireless Internet Wiki to share my information on getting local SIM cards for Internet access. The site has been quite successful and in the meantime many people contribute.
But local SIM cards are only one piece of the puzzle. There are lots of other things one can do besides and on top of this but I never had the courage to write all that stuff down. Now Andrew Grill over at London Calling has done it and it's a great guide in 2 parts (here and here) on how to save on communication costs when traveling. Very well done, I don't have much to ad to it, except perhaps rebtel.com which I use frequently to make International calls from my mobile phone while in my home country.