Free Kontakt version of the Concertmate 300 (You might remember it from Casio or Tandy) for some Chiptune sounds. Get it from Sonus Instruments.
This might be the craziest library for Native Instruments Kontakt that you can find. It´s from Embertone and it´s free.
..is a free MIDI sequencer for NI Kontakt from Home Grown Sounds.
2 Free Kontakt instruments (Toy Piano, Synth). Click pic.
Waves Factory have a bunch of Freeware plug ins and Kontakt libraries
“Piano in 162” is a free sample library of a Steinway Model B grand piano, available in Kontakt, SFZ, and Korg Kronos formats. Click Pic.
After providing your Email adress you´ll get an 80s FM Piano and a shell patch for Native Instruments´ Kontakt from Tangent Edge. Click Pick.