You can think of RawSugar as a searchable del.icio.us with automagic, hierarchical clustering. (Users can also manually create hierarchical tag sets.) So, instead of seeing a long list of links on the left and a long list of tags on the right, at RawSugar you see a list of links on the bottom and your top-level tag categories on the top. The higher level tags are automatically propagated to the lower level ones. So far there is no way for users to publish their tag sets so others can use them.

I spoke briefly with founder Ofer Ben-Schachar who told me only that the auto-hierarchy infers relationships among mulitple tags an individual gives to a single object and among multiple tags multiple people give to the same object. He says the company has 5 patents.

The site is new and only has a few thousand users and about 15,000 links. It looks very usable. Now we’ll just have to see if it reaches the critical masses…