The talk.origins website has a list of instances of observed biological speciation, in the sense of development of non-interfertility as a result of muatation followed by natural selection. Most of these instances are pretty limited - involving polyploidy, or mutation in a couple of genes, as one would expect when we've had a small number of generations to observe divergence. Nonetheless, they are speciation, according to the standard definition.
There are much more impressive instances of speciation on a near-historical timescale. The most impressive are the development of flightlessness in bird species over a time scale of a few thousand years. Birds that belong to usually sedentary species, such as rails, that arrive on new islands (produced usually by volcanism; it's straightforward to date recently formed volcanic islands), tend to become flightless on a time scale of a few thousand years. The 'just-so' story that explains this is that flight requires a lot of energy, and is needed primarily to escape predators. If there are no predators, birds tend to become flightless very quickly. New Zealand, which had no predatory land mammals at all, was full of flightless birds before the gentle, nature-attuned Maoris arrived and slaughtered most of 'em; so were the Hawaiian Islands. So, if you want macroevolution, we have strong circumstantial evidence bird wings have become vestigial appendages in a couple of thousand generations.
RE: this "standard definition": Are we talking about a moving goal post here? I mean, when did this definition get to be standardized? Just wondering.... Info please!!!
Digressing a bit here, Prof.Re your comment about Trojans.
Nebraska Corn Huskers, before that Nebraska Bug Eaters.
Trojans= USC.
Took me all night to find that out. Had to ask a jock friend.
You are a naughty boy. ;D