ZigTag, a social bookmarking tool that has been in the works for years, has finally launched to the public. Competing with services like Delicious and Ma.gnolia, ZigTag categorizes bookmarks through the use of tags and allows users to share those bookmarks with friends. To set itself apart, ZigTag claims its service is "intelligent" and uses semantic technology to understand the meaning of tags. In essence, ZigTag tags have stated definitions, which the company uses to categorize bookmarks more effectively. ZigTag is available upon registration.