I'm looking for a sonogram (spectrogram) VST or DXi plugin. Any help would be appreciated. (preferably one with a large window)

Dunno what your requirements are, but you could search for an old demo of Cool Edit Pro and use it's spectrogram view.

A spectrogram shows the frequency components of a complex wave.

Adobe Audition (Cool Edit's Successor)

"Frequency space editing: Visually isolate and select sounds in frequency and time using a marquee selection tool in the spectral editing view, and then clean up, modify, or apply effects to the selected sound."

http://www.adobe.com/products/audition/overview.html

Havent heard of any others lately...
(Antique Cool Edit would cover you as well)

LCL

I never used the Spectral View in cool edit. I still use CEP2 for the noise reduction. There's a few meters out there...although this doesn't have spectral, I've been using Pinguin Audio Meters for years, Has PPM, RTA, Scope and one of the most important meters...correlation.