Seven Phases has introduced Spectrum Analyzer as a free download.
Here's what they have to say about it:
Spectrum Analyzer is a real-time spectrum analysis VST plugin. The idea was to create an old-fashioned tool reminiscent of classic hardware analyzers of the earlier centuries. Another unique (and quite experimental) feature of the plugin is its detached spectrum display window, freely resizable independently of host application capabilities.
Gaz Williams has one and he brought it round