Thanks for the insight everyone!
I was also thinking about the possibility of canonicalizing them to pages on the ecommerce site, but am afraid that might have the same detrimental effect as redirecting them.
@Nakul and Todd: The content is not horrible, but they are basically set up as blog rolls. I don't think anyone particularly "likes" the content nor do they share it. For the most part, they are product reviews and announcements from our manufacturers, and I have stopped adding content to the sites because it seemed like a waste, when I could be generating new and better content for the actual e-commerce site and our real blog. That said, there is a tremendous amount of content on these sites from the last 4 years. It was apparently working very well for the company, but not after panda and penguin. Some of the domains are exact matches for our head keywords (that we lost rankings for), others are exact matches for product titles or model numbers. I don't think there was ever an unnatural links warning from Google, but I've seen sites not get a message in GWT but still clearly be penalized for it.
@Moosa: Both. Failed in terms of not generating conversions (or possibly generating a few here and there), but relative to the likely negative effect, I'm just not sure how to handle this. They are our sites, so dissavowing them wouldn't do much good. I could go through and manually remove links and canonicalize them, but I'm wondering if it's better to just take the sites down...