MAA/AMC has published answers to 2010 AMC8 contest here.
How to prepare for AMC 8?
I highly recommended
Amazon for only $21.95. It is perfect for AMC8 or AMC10 or Mathcounts contest preparation. My child's school's Math club uses it, everyone LOVES it.
I also recommend the following blog post which has some past actual AMC 8 questions and answers posted, plus recommended books to help educate your child's math, at all levels - from elementary to high school -