Kew's Interactive Key to Genera of Euphorbiaceae s.l., Salicaceae & Achariaceae is available using the following link:
http://keys.lucidcentral.org/key-server/player.jsp?keyId=66
NEW 31st May 2013: I just noticed today that the regular link through to the Key, which is based on a server in Brisbane, seems to have been interrupted by a request for something called a UQ (University of Queensland) Login. I've asked our contact at Lucidcentral for clarification. I'm sorry if this is causing any inconvenience. Sue.