I was surprised to find very nice comparative drug plan information for DW's needs through this site: Medicare.gov: the official U.S. government site for Medicare
You only have to supply your ZIP and your list of prescriptions you are on. You can save the prescriptions data for future uses. Here is a very short cheat sheet
showing how I used this for DW's selection of a drug plan. This is just a subset of what is on the site. The final results information showed us the total annual costs for the plans and lots of other detailed info if needed.
Select "Find health & drug plans" (in one of the gold labeled areas)
Put in ZIP code, click "Find Plans"
For quickly getting to just drug plans select the "I don't know..." options and "Continue to Plan Results"
This is probably the hardest work. Create a drug list. When you save it you will get a drug list ID number. Record it and the date. The date is your password date which you'll need if you come back to this later. If you already have the drug list just enter the ID number and password date and the old list will be retrieved, ready to be updated if need be.
The next step is to select one or more pharmacies. You will be able to see the total cost for each pharmacy and plan later on.
At Step #4 click on "Prescription Drug Plans" and "Continue to Plan Results". Now you will see all the drug plans. The initial ranking is by estimated annual total costs.
I was walked through the Medicare.gov site by a 3rd party provider that my previous employer gives me access to. I never would have know I could do this stuff so easily.
Maybe this info will help others. Sorry if this is already well known but I was certainly not in the loop.