Where can I find current downloadable tower, ground and approach frequencies for USA airports?
I have found something that will work. It is not pretty and I swear I can still smell the punch cards that produced the text files, but here it is:

https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/NASR_Subscription

It is free, it appears to be updated by the FAA, (I verified it has the current frequency for my local VOR that I know changed 2 months ago) and it is searchable.  

Download the current zip file, use the .txt data layout files to determine where in the fixed length record of whatever file your desired data resides in is located.  I did a quick import into Excel and am able to strip the information that I need out based on position in the field. 

Not the pretty spreadsheet I was hoping for, but ...

Thanks for the suggestions, everyone. If anyone knows any standard software for the NASR subscription (or what the !@*# NASR stands for), I'd be interested.