I came across this on the iPad when it showed up in the iBook store.

http://itunes.apple.com/us/book/loud...03510192?mt=11
Basically its an iBook with videos walking through various ad campaigns created by this agency.
Its got some great examples that can offer inspiration for you.
You can also get the videos online:
http://www.ogilvyaction.com/LouderTh...Home.aspx?pg=0