The UNEP News Centre has a press release and lots of links on the Billion Tree Campaign. This
“encourages the planting of indigenous trees and trees that are appropriate to the local environment, with mixtures of species preferred over other options. The campaign identifies four key areas for planting: degraded natural forests and wilderness areas; farms and rural landscapes; sustainably managed plantations; and urban environments but it can also begin with a single tree in a back garden.”
Wangari Maathai, the Prince of Monaco and ICRAF are involved. Go to the website and make your pledge!