New speciations among Darwin's finches
According to oneZoom.org (see the node of interest here), the large ground finch and the large cactus finch share a common ancestor about 170k years ago. Looking among Darwin finches on oneZoom.org, I could not find a more recent speciation event. I could not find their references for their estimates though.

However, part of the difficulty here lies in the exact definition of species one is willing to use (see this post). While it is not reported in oneZoom.org, grant and grant (2009) reported an evidence of reproductive isolation within the G. fortis species.


  Speciation, the process by which two species form from one,
  involves the development of reproductive isolation of two divergent
  lineages. Here, we report the establishment and persistence
  of a reproductively isolated population of Darwin’s finches on the
  small Gala´pagos Island of Daphne Major in the secondary contact
  phase of speciation. In 1981, an immigrant medium ground finch
  (Geospiza fortis) arrived on the island. It was unusually large,
  especially in beak width, sang an unusual song, and carried some
  Geospiza scandens alleles. We followed the fate of this individual
  and its descendants for seven generations over a period of 28
  years. In the fourth generation, after a severe drought, the lineage
  was reduced to a single brother and sister, who bred with each
  other. From then on this lineage, inheriting unusual song, morphology,
  and a uniquely homozygous marker allele, was reproductively
  isolated, because their own descendants bred with each
  other and with no other member of the resident G. fortis population.
  These observations agree with some expectations of an
  ecological theory of speciation in that a barrier to interbreeding
  arises as a correlated effect of adaptive divergence in morphology.
  However, the important, culturally transmitted, song component
  of the barrier appears to have arisen by chance through an initial
  imperfect copying of local song by the immigrant. The study
  reveals additional stochastic elements of speciation, in which
  divergence is initiated in allopatry; immigration to a new area of
  a single male hybrid and initial breeding with a rare hybrid female.