Here is some information from the Tagul website:
Tagul is different
…Wordle clouds cannot be used as in the way tag clouds are usually used, like being embedded on a web page and serving as navigation units. That leaves the niche that Tagul is intended to fulfil. Tagul clouds are not toys and designed to be used on blogs, web pages or any kind of sites as a replacement of ordinary tag clouds. Each tag in Tagul cloud is linked with an URL and is “clickable” that enables visitors to use it for navigation.
Tagul looks to be another useful resource for the toolbox.