Shaun Tan's (ALMA 2011) site is full of interesting information and news: www.shauntan.net.
Katherine Paterson's (ALMA 2006) site has been named after her most famous book, you'll find it at Terabithia.com.
Ryoji Arais (ALMA 2005) site is mostly in Japanese, but even if you don't read Japanese, you can still enjoy the large display of his artwork. All you want to know about Philip Pullman (ALMA 2005) you will find at philip-pullman.com.
Lygia Bojunga (ALMA 2004) started a publishinghouse with the help of the award money. More info on Casa Lygia Bojunga.
Banco del Libro (ALMA 2007) and The Tamer Institute (ALMA 2009), the two organisations that have so far received the award, have official websites. But Christine Nöstlinger, Maurice Sendak and Sonya Hartnett do not have them - yet.