To find literature I use a set of different search engines (Pubmed, Google Scholar, ACM.org, etc). Sometimes directly at their website or through literature managers such as, Jabref and Mekentosj Papers. The latter is great, since it captures the pdf locally.
Then I use connotea, citeulike, and WikiPathways to order my collection. Recently I even started using twitter to manage literature annotations.
Still it happens, even often, that I "loose" papers. I know that I have read a paper, but I don't manage to find it again. I forgot under which label or where I had stored it, or even that I had annotated it.
With all the technology in place, I am still not able to track literature completely.
That is why I am looking for other approaches to optimize my literature management strategy.