We have just rotated the 10 free Champions and announced the next couple of weeks of Champion rotations. The new 10 free Champions are:
Annie Mage Cho'gath Tank Evelynn Melee DPS Janna Mage Malphite Melee DPS Morgana Support Rammus Tank Sivir Ranged DPS Veigar Mage Poppy Melee DPS
Ashe Ranged DPS Kayle Tank MasterYi Melee DPS NuNu Tank Ryze Mage Taric Support Teemo Ranged DPS Tryndmere Melee DPS Zilean Support Nidalee Melee DPS
Amumu Tank FiddleSticks Mage Heimerdinger Support Katarina Melee DPS Sion Tank Soraka Support Tristana Ranged DPS Twisted Fate Ranged DPS Warwick Melee DPS Mordekaiser Melee DPS
I'm also dropping a chart of past rotations, but I've cut out the first couple weeks (it was getting too big) and introduced a count of how many times each Champion has been free (to please the stats followers). The Heroic/Epic/Legendary analysis is based on RP prices - if people would rather have IP prices then speak up (opinions were divided last week).