My experience ...
I recently enjoyed using and exploring the bookmarks on Delicious. I have been using it for accumulating many helpful and interesting tips, tricks, and advice for using social media technology in general and for libraries and have to say WOW!!!
Delicious has been out there for a while and I had dabbled in it in the past, but not as thoroughly as list last time, the discovery experience is unmatched in my opinion. This is the most fun on the Internet I have had in a long time. It is reminiscent to using maps or an atlas, where you start in one location and start allowing your curiosity of a nearby geographical structure, a city, or a highway to take you to different locations and look for other interesting aspects of those areas. In the same way you can start out looking at a road atlas, looking at Eastern Washington and finding yourself perusing the Rocky Mountains or the Gulf Coast in the southern United States, you can find yourself exploring and following tags through the Delicious universe of information.
I started out following tags while completing my class assignment and found myself exploring and experimenting with Tag Galaxy. This site is a tag cloud search service using a relational visual interface to search and display images and photos on Flickr. Since this visual interface is not new, you may say, "what's sooooooo special about it?" It is interesting because its not just circles surrounding another circle with your original tag cloud search, it is depicted as a solar system. Your initial search is the 'sun' and the related tags are orbiting 'planets'. By holding your cursor over a 'planet' the number of photos with that tag is shown. Clicking on a planet changes the 'sun' to those specific tags and clicking on the 'sun' will allow you to browse the pictures with that specific tag.
I found some breathtaking sunset photos of the Washington Palouse. If you cannot initially think of tags to search, try clicking on the suggestions on the left of the screen. This was only one site I found by exploring Delicious.
This brings up another point I would like to touch on, the act of tagging and how it is used to categorize content. Following tags, as I did, can lead to a serendipitous experience, but that is not always the case. Social bookmarking sites are useful, but only as useful as the way tags are applied. Without a specific set of standards to apply tags there is a great deal of subjectivity applied to how content on the Web is categorized and organized with these services. While this can be interpreted and good or bad, it does make using these types of services more of a wild card than a tried and true method of discovery.
Some final thoughts: I quiet enjoy the serendipitous discovery of content by using services like Delicious and tagging and social bookmarking services will be invaluable to me in the future.