For those of you experiencing this assault upon your blog, see the FAQ My Blog Has Been Hijacked - What Do I Do? for current diagnosis and removal techniques. Note that the gadgets noted this week, as earlier, appear to resist removal, so you'll probably need to use "Edit HTML", and delete the offending code.
(Update 2010/03/23): Blogger Support has taken ownership of the problem.
Our team is working to sort out these affected gadgets from our side, and hope to have this fix out shortly.