Evolution as a fact
Evolution is a fact in the same vein that gravity is, yet the so called "theory" of evolution deals with why, or how, it occurs, much like the theory of gravity does as well. Newton's law basically applies to the physics of objects caught in gravity, not why or how it occurs specifically.
That said, the facts that build the backbone of the theory of evolution are:
1. Speciation[1]: It has occurred in our lifetime in labs.
2. Fossil record[2]: Thousands of intermediate fossils found. Not to mention that to falsify ToE all you would have to do is find a rabbit or [3]hare in the Cambrian, yet to this day, the finds in the fossil record form a natural hierarchy with simple organisms first and more complex organisms found as you continue.
3. Genetics[4]: Comparing the genome between species forms a complete family tree just as Darwin predicted. We share around 95% of our DNA with chimpanzees, even less than that with Gorillas, even less with other mammals, and even less with reptiles and so on.
4. The age of the Earth[5]: 4.5 billion years old. This gives plenty of time for evolution to occur as predicted, and even creationists acknowledge variation via adaptation to have occurred within "kinds"(which is a purely religious word) yet do not follow it to the logical conclusion which is exactly what evolution suggests.
With all that said, ToE is a simple yet eloquent theory that explains the diversity of life. Variation occurs because of genetic components and successful variations are not random, but selected by an ever changing environment. Those who adapt successfully survive, those who do not, don't.
References:
[1] http://news.bbc.co.uk/2/hi/science/nature/3790531.stm
[2] http://en.wikipedia.org/wiki/List_of_transitional_fossils (with its own set of cited references)
[3] http://www.time.com/time/magazine/article/0,9171,1090909-6,00.html
[4] http://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html
http://richarddawkins.net/articles/605361-it-started-with-a-shrew-study-maps-the-primate-family-tree
[5] http://pubs.usgs.gov/gip/geotime/age.html