@OP I ran across Richard Dawkins’ analogy of natural selection as “climbing Mount Improbable.” In that memorable and vivid metaphor, Dawkins illustrates the truly incremental and gradual nature of the evolutionary process. Opponents of evolution have contended that, while change within species can occur, the leap from one species to a new species is just too improbably great to have happened by purely natural processes. Outside assistance must have been involved.

I was just refuting this assertion on the "Unbelief in the Pews" discussion, Where one of the best arguments countering claims based on the absence of fossils in sediment layers, and a misinterpretation of "Punctuated Equilibrium", is to look at present-day on-going divergent evolution. Ring species such as Gulls are a very good example:

http://en.wikipedia.org/wiki/Ring_species - A classic example of ring species is the Larus gulls' circumpolar species "ring". The range of these gulls forms a ring around the North Pole, which is not normally transited by individual gulls.

The Herring Gull L. argentatus, which lives primarily in Great Britain and Ireland, can hybridize with the American Herring Gull L. smithsonianus, (living in North America), which can also hybridize with the Vega or East Siberian Herring Gull L. vegae, the western subspecies of which, Birula's Gull L. vegae birulai, can hybridize with Heuglin's gull L. heuglini, which in turn can hybridize with the Siberian Lesser Black-backed Gull L. fuscus. All four of these live across the north of Siberia. The last is the eastern representative of the Lesser Black-backed Gulls back in north-western Europe, including Great Britain.

The Lesser Black-backed Gulls and Herring Gulls are sufficiently different that they do not normally hybridize; thus the group of gulls forms a continuum except where the two lineages meet in Europe.

If at some time in the future fossils of Black-backed Gulls and Herring Gulls were found at a single location, no intermediate forms would be found at that location - they would be hundreds or thousands of miles away!