If you have not read the book I highly recommend it. This book was definitely one of my top reads in 2010. It's the kind of book that acts like a swift wind to clear the smog of the world and help deliver a clear view for what needs to happen in our lives as believers. At least that was my experience.
Here are the five challenges (with my explanations in parenthesis):
1. Pray for the entire world
2. Read through the entire Word (use a systematic plan)
3. Sacrifice your money for a specific purpose (beyond your regular giving, give up something specific)
4. Spend your time in another context (think mission trip or more, get out of your comfort zone)
5. Commit your life to a multiplying community (whether small group or church, plug in and grow AND grow the group)
For details and the full deal see www.radicalthebook.com