If you happen to own the original Orcs Must Die! on PC (which you probably should), you'll unlock a bonus gametype in the sequel. Orcs Must Die! 2 will include a 'Classic' mode that features the ten levels from the first game, remixed with new enemy types, items, weapons, spells and traps. Players who haven’t yet downloaded Orcs Must Die! can pick it up for a limited time for 50% off on Steam, or wait for an inevitable daily deal/end of sale reduction [ta Crazy Jamie].
Robot Entertainment's tower defence/action hybrid will release on July 30th - packing the cooperative multiplayer we sorely missed in its predecessor. More details here.