Norwegian newspaper DagBladet is reporting DLC will likely be available day one or soon thereafter for Mass Effect 2. DagBladet says the usual items like armor and weapons will be available, but also other things, such as an unlockable planet and even a new ally by the name of Zaeed Messani, the grizzled bounty hunter pictured above. The piece also mentions an in-game store for unlocking DLC called "Cerberus Network," which sounds a lot like Dragon Age: Origins' DLC platform.
There's more info available, but in the interest of being as spoiler-free as possible, we won't go into it. So, if you don't mind braving spoiler territory, hit up the link below.