Past Horizons Projects page gives you a wealth of information about all the projects happening around the world, from Scotland to Peru and Across the USA to China.
If you are interested in getting involved, then this is the place to be - with over 350 to choose from in a range of sophisticated but simple to use search types
http://www.pasthorizons.com/worldprojects Past Horizons also has a free to read quarterly online archaeology journal which concentrates on field schools and volunteer projects around the world.
http://www.pasthorizons.com/magazine