On: Counting Billion Distinct Objects Using Only 1.5KB of Memory (2012)

[Radim]

For Python, there's Bounter, "Efficient Counter that uses a limited (bounded) amount of memory regardless of data size."

https://github.com/RaRe-Technologies/bounter

Apart from HyperLogLog, Bounter implements a bunch of other nifty (fast) approximate counting algorithms like CountMinSketch.