One is a gadget called Popular Posts that lets you post links to your posts that had the most visitors. New visitors can get a feel for what your readers enjoy.
Another is Link List, which I've covered briefly in another context. This is where you link to some of your personal favorites, so you can direct your readers to some things you think are important.
From this point forward, all references will be to the new Blogger interface.
Pull up the Layout page, then click Add a Gadget.
Choose Popular Posts.