I have been seeing many blogs including a "You might also like..." section in below each post. This has been racking my brain as to how to do it for a while now as it seemed too easy to not do, but I just didn't know how to implement it. Part of my problem was I didn't do the obvious thing until today, I googled it! Sure enough I came across LinkWithin. It's a widget you can add to your blog that will evaluate your website and creates the suggestions for you.
I actually thought that it was something that I had to choose what my current post relates to, which becomes increasingly challenging as your blog archive grows. You install the widget (which was super easy for me under blogger) and it does the rest! There is no thinking on your part to do, just write your posts as normal. LinkWithin even has detailed easy to follow instructions for you to follow.
Check it out, and let me know if it worked for you.