Zigtag is an intelligent, semantic, social bookmarking service. The Zigtag sidebar provides both an intuitive way of tagging web pages (using descriptive words or phrases) and a user-friendly way of quickly retrieving tagged pages.
Users tag web pages with semantic tags (tags which have definitions) e.g. if you tag a page with “Apple” you can choose “Apple (computer company)”, “Apple (fruit)”, “Apple (record label)” etc. Pages can be retrieved using any of the tags which were previously entered or using synonyms for those tags, e.g. a page tagged with “Car” can be retrieved by searching for pages tagged with “Car” or “Automobile” (Zigtag understands Car and Automobile are the same). This allows you to:
Zigtag also has a major social networking component; you can see what your friends are tagging and create and join special interest groups. The sidebar notifies you when your friends tag something new, and a news feed allows you to see what your friends are tagging at a glance. It’s kind of a “personal Digg”—your friends’ interesting sites are likely to be interesting to you. Zigtag groups form the focal point for collaboration and a central gathering point for people with shared interests.