The International Congress of Mathematicians (ICM) proceedings have been digitized back to the first volume in 1893, and these ICM Proceedings 1893-2006 are now freely available online, courtesy of the International Mathematical Union.
As you can see in our OskiCat record, the Mathematics Statistics Library will retain its print collection of these proceedings, and we have already ordered the 2010 Proceedings, soon to be published by World Scientific.