The 2008 winner of the CILIP Carnegie medal was Philip Reeve, for his book, 'Here Lies Arthur'. For more information about this author, have a look at the Scholastic Children's Books Author Zone.
The Walker Books website has a author and artist section well worth a browse.
Have a look at the CILIP Carnegie and Kate Greenaway medal website for recent shortlists and winners.
There is an Official Roald Dahl website with photos, interviews, tips for teachers and an enquiry feature.
Have a look on the Wordpool website for links to websites of popular UK children's authors, including Malorie Blackman, Gillian Cross and Ann Pilling.
The Children's Book Council lists links to hundred's of U.S. children's author websites.
When children ask about authors you may not be familiar with, it's always worth typing the author's name into Google - they may have their own website!