There are XPRL tags, Technorati tags, Social Media tags, bar coded tags, part of speech tags, and they all mean something. This article in New Scientist offers a spooky insight into where all this might lead us.
Social media tags are all over the place and here are some social media vendors that use them:
- Del.icio.us - A social bookmarking site that allows users to bookmark many sites and then tag them with many descriptive words, allowing other people to search by those terms to find pages that other people found useful.
- Flickr - A service that allows users to tag images with many specific nouns, verbs, and adjectives that describe the picture. This is then searchable.
- Gmail - A webmail site that was one of the first to allow categorization of objects using tags, known as "labels" on emails.
- LibraryThing - A social book cataloguing and community website, tags feature heavily here.