The grandfather of social bookmarking sites is del.icio.us, which basically brought “tagging” mainstream (along with Technorati). Most people I know who use the service end up with unwieldy tag clouds, however, because it’s often hard to enforce a self-discipline on what tags you assign. I’ve spent a lot of time manually pruning my tags but there are still plenty on my tag list that are redundant or obsolete.
There is an option to “bundle” your tags – essentially, tagging a group of tags, to help you organize things better. However, bundles at present are only visible to the user, and do not have a dedicated URL or RSS feed like individual tags do. Using the “+” operator to search for multiple tags, ie http://del.icio.us/azizhp/Iraq+Hillary, functions as an AND operator, whereas to simulate a bundle you’d need an OR equivalent that del.icio.us does not support. As a result, if you want to add a linkroll to your site that only shows tag from a single bundle, you’re out of luck.
However, there is a workaround, albeit a clumsy one: create “container” tags. Then you must manually tag all items in the bundle with the container tag. After doing this, you will be able to access your bundle using the container tag, and can create customized linkrolls accordingly. For example, I created the “2008” container tag for all my tags related to the Presidential candidates.
One caveat: try to avoid naming your container tags identically to the bundle. You can prefix the container tags with the “@” symbol to keep them distinct, or name them entirely differently. This is so that if/when in the near future del.icio.us improves support for bundles there won’t be any namespace collisions between your tags and your bundles. Once that day comes you can simply delete all the container tags if you so wish.
Alas, there still is no way to create a tag cloud from a single bundle, so that still awaits the del.icio.us team’s attention.