Much like the traditional practice of placing a mark in a book to hold our place, bookmarking on the Internet allows us to mark our place on the web for future reference. Bookmarks are the terms used in the browsers Netscape Navigator, Firefox and Opera. Internet Explorer uses the term Favorites.

When you bookmark a web site, your browser saves the information on your computer. This poses a problem when you are looking for a site while using a different computer. Given that most of us use at least two different computers each day (one at home and one at school or work), this is a significant problem. One solution to this problem is to use a Web-based application to store your bookmarks. In this scenario, when you want to retrieve a bookmark, you access the web-based application from any internet connected computer with your unique login and password.

These bookmarking services have become quite sophisticated. One of the more interesting advances is the capacity to share your bookmarks with others. Delicious is the most popular example. When you bookmark a site using Delicious, it is available for anyone to view - provided they know your username. To see an example, check out my bookmarks: http://del.icio.us/iteach.

Another important advance is the use of tagging to organize bookmarks. Most earlier systems used classification systems that forces sites into one category. This approach doesn't mesh well with reality where any object can take on any number of classifications. Tagging improves upon this by allowing you to tag a site with multiple tags. For example, if I was bookmarking this site, I might use the tag bookmarking or 709 (the course number of a class I teach entitled Internet for Educators). Fortunately, with tagging, I don't have to choose between the two classifications, I can use both.

Combining usernames with tags gives you a powerful tool to share bookmarks for specific purposes. If I would like my students to visit some excellent math sites, I would use the URL http://del.icio.us/iteach/mathematics.

Another mechanism for sharing bookmarks is through the use of a linkroll embedded into a web page. This has the advantage of integrating the bookmarks in to a site rather than sending the user off to another site. Below you can see a linkroll of my sites tagged science.

By sharing bookmarks, these sites become very useful search tools. Searching Delicious for science sites can be quite fruitful. Most of the results you get from a search have been bookmarked by hundreds, if not thousands, of other users. In other words, you are getting only sites that people bookmarked - a good indication that they are worthwhile.

Another method for discovering helpful sites is to identify users with common interests. The popular sites that they have bookmarked may often suit your needs as well.