Observed evolutionary events and speciation.
Definition of evolution - A change in the gene pool of a population over time. One example is insects developing a resistance to pesticides over the period of a few years.Another would be microbes developing a resistance to antibiotics.A third would be the continual mutations of viruses.The domestication of animals is also a telling example,with humans providing the selective pressure rather than natural events.The fact that this is an intelligent application of the theory neither invalidates the theory of evolution nor provides evidence for so called "Intelligent Design", as you well know Clanad.
The origin of new species by evolution has also been observed, both in the laboratory and in the wild. See, for example, (Weinberg, J.R., V.R. Starczak, and D. Jorg, 1992, "Evidence for rapid speciation following a founder event in the laboratory." Evolution 46: 1214-1220)
Evolution makes predictions about what we would expect to see in the fossil record, comparative anatomy, genetic sequences, geographical distribution of species, etc., and these predictions have been verified many times over. The number of observations supporting evolution is overwhelming.What hasn't been observed is one animal abruptly changing into a radically different one, such as a dog changing into a giraffe. Evolution doesn't propose occurrences even remotely like that.
Speciation - There are indeed many different definitions of speciation, but thesedefinitions are largely due to the differences in reproduction between the major types of organism... plant, arthropod, invertabrate, mammal and their types of reproduction ( self pollination, asexual, sexual etc). That doesnt mean to say that no examples can be found. Such examples can be found amongst plants ( evening primrose, goatsbeards), insect (drosophila), mammal (faroe island mouse), fish (cichlids)