I use the Most Popular Posts Widget that helps to bring up old Posts based on what people read - I get a high %% of search engine traffic so this seems to help.
Other people put a text widget in the sidebar and put links to old Posts they think are relevant or are the most popular based on the Stats page
I'm not sure I want to merely use the Most Popular Posts Widget --that just gets people perhaps to only the posts that continue to be read.
I like some of my most popular posts but there some others I've written where I did spend decent time and am proud of /think they are quite good.
I'm trying a range of different things --
RSS feed based on a common tagged topic theme
Another widget with select posts. It seems it only gets some people, not alot, motivated to take more steps to click and look around.
This is why I am on a lookout for new themes that show a preview of related photo to older blog posts. I'm fine with my present theme and certainly am willing to hold for awhile before another meets my needs.