Google is gradually rolling out a new Gmail people widget that lets you view recent Google+ posts within Gmail.
To see these Google+ posts from the sender of an email, you have to be a Google+ member and the sender has to include you in a circle. This limits what you see, but Google may relax some of these requirements when its social network goes public.
This feature is gradually rolling out so if you don't have this Google+ integration yet, be patient. It's coming soon.