  I discuss novel QCD phenomena recently observed in p+p, p+A and A+A
collisions, that result from the non-linear dynamics of small-x gluons. I focus
on di-hadron correlation measurements, as opposed to single-hadron observables
often too inclusive to distinguish possible new effects from established
mechanisms. Specifically, I discuss angular correlations of forward di-hadrons
in d+Au collisions and long-range rapidity correlations in high-multiplicity
p+p and Au+Au collisions.
