I attended a lecture just a few weeks ago on observed speciation in mosquitoes, from a team at the University of Texas at Austin.
A graduate student took a trek through part of Africa, capturing mosquito samples every few dozen miles. These mosquitoes were all part of one particular species, but of course there were mutations between particular mosquitoes. Specifically, some mosquitoes had part of their DNA "inverted" -- it was in the chromosome backwards. It was a common mutation.
Next, they observed the mosquitoes mating between each other. Somehow, that mutation expressed something that the mosquitoes could notice: the vast majority of the time, those with the inversion mated with each other and not other mosquitoes. Now, a few mated with other mosquitoes, but most didn't.
What will this lead to? In perhaps just a few hundred more generations, those mosquitoes won't be mating with the other groups at all. They'll only mate with ones sharing their own mutations -- and the group will have developed its own specific mutations and characteristics as well. As we watch, they're becoming a new species.
Now, this isn't published yet: when I attended the lecture, the data was just a few weeks old. As for interesting published material, try this: http://www.newscientist.com/article/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html
Bacteria suddenly evolved the ability to metabolize citrate, an ability they did not have at all before. A new ability developed in the lab, under our noses.