The true religious believer believes that God created the Earth and the heavens, in much the same form as they take on now, about 6,000 years ago. They do not believe in evolution, even though the proof is, quite literally, all around them. Yet, they believe in creationism which lacks any proof whatsoever.
Everything around you is evidence of evolution. Everything. Every animal, every germ, every person on this Earth. Everything can be shown to be the result of millennia of evolutionary processes. I won’t bore you with millions of examples of how evolution exists (which I could, if I had to – the creationists can’t give you even one that supports their world-view), I’ll just mention a few of the more interesting examples:
You’ve probably eaten an orange at some point in your life? Probably dozens or even hundreds, maybe even thousands. Well, have you ever eaten a navel orange? Those are evidence of evolution right there in the palm of your hand! You know, navel oranges are those ones without the seeds (well, they actually do have itsy-bitsy little seeds that don’t function, but we’ll say for argument’s sake that they are, in effect, seedless), they have that tiny little (little-orange-tumor-like) second orange growing within the larger one. That’s why they’re called ‘navel’ oranges – the second, baby-orange produces a little ‘belly-button’ or 'navel' on the orange's rind.
You’ve probably eaten hundreds of navel oranges in your lifetime. Well, you could say that all those navel oranges you’ve eaten, every single little one – as well as every navel orange everyone else on Earth has ever eaten – came from that same tree! Every single one of 'em!
That is precisely because of the theory of - no, the fact of - evolution (or, more specifically, man’s manipulation of evolution). Evolution works by random mutation.
Every once in a while, a random mutation creates a slightly different offspring in the population. If that mutation is bad, the offspring will likely have a lowered chance of reproducing (you don’t see women drooling over mentally and physically handicapped men, to point out a single human example).
However, if that mutation is good, it might lead to an increased chance at reproduction. And, over generations, that mutation will work its way through the population until it becomes the norm, until it takes over.
In 1820, a regular-looking orange tree in an orchard in Brazil grew from a mutated seed and ended up producing what we now call navel oranges. This was a very bad mutation – as it made the tree sterile (there are no seeds in a navel orange, and it therefore has no means of reproducing). Normally, a sterile offspring would die out, never to be seen again. A forgotten path on the road of evolution. But, human beings have learned to bend evolution to our whims (in certain circumstances anyways). We’ve learned how to, literally, play God in some cases. This bad mutation, that should have ended up on top of evolution’s garbage-heap, ended up being very good for humans after all, as no longer did we have to worry about breaking a tooth on an orange seed ever again! The mutation produced sweet, juicy, seedless navel oranges.
The demand for navel oranges skyrocketed around the globe, and cuttings from the tree have been transported and planted in organge orchards worldwide (cuttings can be grown into full-sized trees). And, each of those trees has the exact same DNA as that original 1820 mutant tree from Brazil.
Since each of those trees was grown from a cutting of the original tree, you can say that every navel orange the world has ever known - came directly from the branches of that one single tree!
I find that kind of beautiful and wonderous, don’t you? Billions and billions of people on Earth - yet we’ve all eaten the fruit of the same tree…
Creationists believe that God is 100% perfect and created the world pretty much exactly as it is right now 6,000 years ago. If that was the case, the navel orange shouldn’t exist! It just shouldn't be here. The Atheists must be right.
Mutations shouldn’t happen in God’s world (mutations would be an utter abomination). But they do. And, evolution explains them perfectly – in a way that God never,ever could.
Every navel orange you’ve ever eaten is proof of evolution’s power and beauty (and of man’s incessant ability to toy with the world around us).
The closest a creationist will ever come to explaining the existence of the navel orange – is that the random mutation that created it - happened in a quaint little orchard - near a monastery!
-- Read the rest of God on Trial: The Case Against Religion, an Atheist's Debunking of Religious Dogma at Simiantology.com
Spirituality 
Although I do believe in much of the evolutionary process and prefer to believe that much of the Bible is allegory in order to explain complex processes to people lacking the knowledge to understand them (meaning, the time of the original writings), I find your use of the navel orange somewhat lacking - enlightening in some respects, but lacking in others. Evolution is change - mutation is change. Because of mutation, the world has changed. But, in ever instance, those mutated species have had the ability to reproduce, the ability to become the dominate or better adapted species. Not so with the navel orange. Without man, as you pointed out, that species would have died out. It was very fortunate that someone was on hand at the time of the mutation who know about cuttings.
But, the original orange still exists. The navel orange was not an improved species - it was, in fact, a defect. One that should not have been capable of reproduction. An evolved species usually becomes better adapted to live in its environment. That was not so with the navel.
If your proof was that it was a verifiable instance of spontaneous mutation, then it was a good one. People do need to see that something usable (as it were) can come from a mutant - that mutation is not always bad for us. But, I see this history of the navel better used to argue against the church's opposition to artificial insemination and invitro fertilization than I do proof of evolution.