The current MSAR is 2008-2009. It compiles data from the class which matriculated in Fall 2006. It came out in May, about a month before the AMCAS app opened for the class which will matriculate Fall 2008. So the '08 MSAR is aimed at the '08 matriculating class.
They don't change very much, year to year. Almost any med school is going to have more recent, in-depth and/or relevant data on its website. So a good way to start thinking about schools that you're interested in is to use the MSAR to make a shopping list, and then directly research the schools you like.
You can find one in a library or in an advising center. If you really want to buy one (I did) and you're applying next year, the '08-'09 version is fine to get you going. Before you hit submit next year, you can find and browse the new version as a final editing pass on your school list.
Best of luck to you.