After blogging for a few months or years a blogger usually writes a lot of posts. Some of them are obviously more valuable then others and it would be a shame if they were very hard to find. One solution to make sure that people will read what you wrote in the past is to actually rewrite your old posts. In order to do this you should use up-to-date information and publish them again. I have seen this done on the top blogs in the blogosphere and if your older posts are able to stand the test of time, there is no reason why you would not want to do it. Very often there is a lot of valuable information in older posts and rewriting them might be a very good idea.
Another approach would be to link to your best posts from the sidebar, but on the other hand rewriting posts might be more beneficial, as it would update them with more recent data. If you do not plan to rewrite your older posts, then you may at least want to link to your best posts on your sidebar. If you visit many blogs, then you will notice that many other bloggers link to their posts from their sidebar.