Google are clearly switching the weight of backlinks vs content. I have several sites built recent that have no backlinks at all, they rank on the first pages for several relatively good keywords, I also HAD Autoblogs, made good from them up untill Panda.
If the content is good and useful to readers, then others will automatically link to your posts and pages over time.
Sure it helps if you do off-page SEO too, but many people over do this, and although most of the people running Google look like clowns, Matt Cu-n-tts springs to mind, they are not so easily fooled nowdays. Content really IS king.
Although slightly off topic, an good example would be Autoblogs, anyone that tells you that Autoblogs will rank good just by posting duplicate content from various sources and then building a massive amounts of links to all posts are either mentally impaired or making money off spamming services. The days of true Autoblogs are over, this shit used to work but sadly making money online with this method no longer is a viable option.
Listen to some of the comments above, and update your content paying more attention to on-page seo, write killer articles that others will find useful, check for broken links on your website etc.
If you obtain good on-page seo, then think about getting backlinks.
Now I'm gonna get screamed at for my whitehat methods, but to truelly understand how to do blackhat, it really helps to start off white
I hope you manage to get your sites back on the first page again.