From Blue Cat Audio:
Blue Cat's FreqAnalyst is a free spectrum analyzer plugin that lets you monitor the spectral content of your audio signal in real time. It has been designed to provide extreme smoothness and high resolution for both time and frequency: unlike most spectrum analyzers, Blue Cat's FreqAnalyst is able to display continuous variations even with a very high frequency resolution, thanks to its unique smooth interpolation algorithms.
What's new in this version:
Version 2.01 has performance improvement when running under high CPU load for other platforms.