There are two great MD/PhD blogs on the internet.  Although they are not updated frequently, they do contain a wealth of information on what it is like to be in an MD/PhD program.  Also provides a lot of commentary on interviewing for residencies as an MD/PhD.  I would highly suggest you go through these blogs if you are considering applying for an MD/PhD program or if you wanted to know more about what the program entails.  I do find some posts very entertaining.  Overall, each blog posting is well written.

1. MudPhudder
2. MudPhud Adventures - Hasn't been updated since June 2009.