CowBoom offers the used Amazon Kindle Fire HD 16GB 7" WiFi Android Tablet for $89.99 with free shipping. That's tied with our February mention of a refurb as the lowest total price we've seen for this tablet in any condition. (It's $75 below the best price for a new one today.) This WiFi-only tablet runs a heavily-modified version of Google's Android OS and sports a dual-core 1.2GHz processor, 7" 1280x800 LCD, and 16GB of internal storage.
Of note, no warranty information is included. Also, this used unit may be missing accessories and have scratches or dents.