On the Blogger platform, tag pages are blocked in the robots.txt so they won't be index and thus, won't cause duplicate content issues (no matter what canonical tags they have on them). Archives seem to get around this issue by creating full html pages; thus, it doesn't show up as duplicate content, but as snippets of content on an indexing page.

Please contact our Help Team help@seomoz.org to help you add your Blogger account as a campaign.

I'd also check out this guide to handling duplicate content.

I'd be careful about hiding text. Google doesn't like that.

I couldn't find anything for bulk checking sites.

However, there's this add-on for Firefox, which checks sites for you: https://addons.mozilla.org/en-US/firefox/addon/wappalyzer/

And someone built this web app: http://onlinewebtool.com/cmsdetector.php

You do have to do it one at a time.