I've gotten a number of questions recently about adding tag clouds to SharePoint. Tag clouds are handy for visualizing content tags in sites, wikis, and blogs.
The Community Kit for SharePoint contains a great Tag Cloud web part...available here: http://www.codeplex.com/CKS/Release/ProjectReleases.aspx?ReleaseId=4820

Check out the entire Community Kit for SharePoint here: http://www.codeplex.com/CKS/. It's a set of best practices, templates, Web Parts, tools, and source code that enables the creation of a community website based on SharePoint technology.