Guys,
This fear about duplicate content is not founded. There was a post from some Google engineer recently that shed light on this issue. This was posted in this
SEO section as well (too tired to go dig it up).
The gist was that unless you are copying the exact same content from another website you will not be penalized. It's funny that people stress so much over this issue of
duplicate content. Ever hear about someone get penalized because they have links to the archives on their blogs ?
Google may weigh some of your content less if it finds it in more than one location... but you will not be penalized. If Google finds something unique it will view it as precious, like a rare gem. If your site only reuses free articles from directories, Google may see it as a "common rock" but will not penalize you. I know this analogy is retarded
. I'm just trying to make a point and you are asking a good question.
When you use rel="nofollow", visitors will still be able to click of course, but Google will be blocked. That means no link juice and no index. But it may be good to reduce the number of outgoing links a page has (say to the archives) because the links that are left will pump more juice.
To answer the last part of your post, sitemaps and internal linking will ensure that all your old posts are indexed (except those that you no-follow). I like submitting my sitemaps to high
PR social media sites so they get visited often by Google. I also include a link to my sitemap.xml in the blog footer.
Hope this helps man, Cheers,
--Sebastien