There is a Civilization bundle on Humble Bundle

You may have read about (or perhaps even bought) The Humble Freedom Bundle, and excellent bundle for $30 or more that is no longer for sale. It's replacement is a Civilization Bundle on offer that sees you net Civilization III and Civilization IV complete editions for $1 or more, while if you beat the average price (currently $8) you also get Civilization V and its two expansion Brave New World and Gods & Kings as well as coupons with 20-25% off Civilization VI. Further more if you pay more than $15 you also get Civilization: Beyond Earth and its expansion Rising Tide (as well as a map pack).

If you've been missing out on some of these older Civ games it might be a good time to catch up...