Possum Possum is a tool that acts as back-up memory for you; it's kind of a personal search engine, remembering what text you've seen on the Internet (E-mail, and other computer documents) and indexing it on ... Cost: $25 Buy full version       Trial version       Publisher: mXac     Descriptions Possum: Possum is a tool that acts as back-up memory for you; it's kind of a personal search engine, remembering what text you've seen on the Internet (E-mail, and other computer documents) and indexing it on your hard drive. That way, a few months or years down the road, when you know you saw the information but are unable to find it, Possum will have a record of it.