Don’t forget del.icio.us! The site that first popularized social bookmarking was awesome before being bought by Yahoo! and being left to die on the vine. del.icio.us was great for seeing content from across the entire web tagged by readers (remember the term folksonomy?) and had convenience features that would be very welcome today:
- Tags had their own feeds.
- Feeds could be for the ‘top’ links only, or of everything being marked with that tag.
- Feeds could also be for a particular user.
- A later refinement allowed tags to be namespaced, so the tech.jobs.python, tech.web and tech.bio tags all implicitly added a tech tag, and subscribing to tech gave you all items in that namespace.
The del.icio.us data was pretty open, and quite a few folks used it for visualizations, Recommender Systems, and the like.
Arguably, among the popular sites, Tumbler comes closest today to the basic bookmarking functionality, as you can 'tumbl' a link and add tags, with or without adding a note, but links are definitely 2nd class citizens compared to content posts, and links that you post in this way aren’t particularly discoverable, even by yourself, making them useless as bookmarks.