Suddenly, I am getting "redirected" to various sites - mostly retail, when I am perusing most of my favorite sites. Did I download some virus!

Try a different browser.

Yep; some sort of malware.

Run malwarebytes.

go to malwarebytes.com and download adwcleaner and malwarebytes. both are free.

run adwcleaner first, scan everything, quarantine and delete everything.

it will force a reboot

then install malwarebytes and scan for anything left.

An AV like Malwarebytes is an excellent start and may be all you need.
However, a few other things depending on your OS.
An infected hosts file could be populated with misdirections.
This needs to be checked > link
Additionally, you should clear your browser cache and also clear your DNS cache .
Also IF you are going to an URL from a saved link, this can be appended and should be deleted.
Enter the URL directly (in browser NOT in a Google search ) and then make a shortcut from any successful entry.
Good Luck