I've just added a swicki to this blog; the best definition of a swicki I can find is on the OSS4lib site. Mine is a little crude, but may develop. I was torn between Eurekster and ZoomClouds, but went for the former in the end: Zoom Clouds does the tag cloud, but not search, as far as I could tell.
Post scriptum: I've taken it of for the time being. The Eurekster version seems to require to be populated manually, rather than build it organically from the blog, tags and searches. Also it slowed the pages down no end.