A while back I found a nifty webpart for our SharePoint WSS site called Tag Cloud which lets you tag documents in your SharePoint site and then display a list of all tags with those that occur more often being rendered in larger text. We decided to use for our application support/help desk sites because it makes finding documents easier. Yes, SharePoint has a search feature and of course we could structure our documentation to make it easier to find stuff but this just seems to be a nice option to have. After installing it though I came across a bug/feature limitation. The "tag cloud" webpart would show tags from documents that may be buried several levels deep in a document library but when you clicked on a tag you would get no results. The solution is modify the source code to include the following:
SPQuery query = new SPQuery();
query.ViewAttributes = "Scope=\"Recursive\"";
Add the second line above after the first line in the SPUrlBrowser.cs and SPTagBrowser.cs files. Recompile the solution and deploy the update SharePoint solution file. Once that is done the "cloud browser" web part will correctly find all items, no matter what level they may reside in. Note that you'll need to make the code modifications from a machine where SharePoint is installed since the solution references the SharePoint dlls.
11-21-2008 Update: I've uploaded my wsp file.