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I've used Delicious for a long time to manage my Web bookmarks. It was easy to use, accessible from any browser, and worked well with Firefox. For all my needs, it was a great bookmarking service. Then I found Diigo, and suddenly Delicious didn't look so good anymore. Diigo is another social bookmarking service (and one we've covered before), offering all of Delicious' relevant features and much more. I left Delicious, and haven't ever looked back. There are a lot of things I love about Diigo, but there are seven features that sold me on using Diigo for all my bookmarking needs. These are all in addition to the features I deem non-negotiable for social bookmarking sites- tagging, Firefox extensions, looking at popular bookmarks, etc.