The products I was promoting were seasonal so as those products are not available anymore websites don't of course can't convert. However if we use an indicator when those products were available it actually converted very well. I was so shocked at first with the results. From that experience I learned that you can sell "anything" to people. The best part is that I used those pages as landing pages for Pay Per Click campaigns and results were even more incredible. CTR was incredible and CR was also very good but we also had some luck with some factors at that point also those offers that are not available today in this way.
I was so busy with other things that I had to leave that strategy but I am thinking to start it again with of course few tweaks and improvments and on new products.
Directory submission is still effective so you can use it. About the dupe content, I can see them also in textlinks.com as my boss subscribes there. Their sites are auto blogs which are getting contents from article directories but I am really surprised that some of their sites are getting high PR's.
You can always build some quality Squidoo lenses and create backlinks, not only you will bring interesting subjects to the Squidoo community but also be ranked in search engines and get a better exposure.
Those who can make you believe absurdities can make you commit atrocities.
Guest blogging is becoming a really popular way of getting backlinks.. it works great because the traffic is on target and is relevent for the search engines.
Look like squidoo hasn't been hit with the "Farmer update" How Demand Media Used PR Spin to Have Google Kill Their Competitors
Recently, I ordered and read a book about a certain marketing niche. Upon completion, i mailed the writer how useful i found some of her ideas and was promptly rewarded by a backlink on her site next to a quote of my letter.
...and some people like to spam netbuilders for signature links
I agree with nicolebeckett about having some quality original content on your site. Although I wouldn't wait around hoping for natural links. Go find old established websites that link out to other resource sites. Then e-mail the webmaster to consider adding your "hobby" site to their list of links. To get away with this, you probably want to hold off inserting Ads on your site, and have a somewhat amateurish look to your site. Get the links and ranking before monetizing the traffic.
Another technique is to link out to hobby sites which have loads of original content and no monetization. Then the webmaster may spot you linking to them and reciprocate. Later you remove your link to get the one-way link back to your site.
You could also hand out award badges to other sites to get them to proudly display a link back to your site.