Commonly, religious discussion turns to the subject of origins. There are two reasons for this: firstly, there are those with a literal or semi-literal interpretation of the Bible (or other relevant holy book) who remain convinced that the world was created in the recent past looking more or less as it does today. Obviously, this issue must be resolved before the existence or nature of the deity can even begin to be discussed! Secondly, even those with the more common, nonliteral interpretation of the creation story often use arguments that aren't valid to insist on direct interference by a deity at one or more points in the past. And while thanks to its flexibility this "tinkering" God theory cannot be ruled out to the same degree as literal interpretation story potentially can, its proponents should still be aware that there's little justification from the evidence for it, and that the majority of the story of our origins can now be explained in a secular manner.
The basic idea: scientific knowledge, as we know it, is not incompatible with a creator. But it most certainly does not require one.
I think it would be prudent to define a few terms first.
Evolution: The change in life over long time scales by descent with modification through natural selection, except when used in astronomical context (where it refers to slow changes in stars and galaxies.)
Creationism: Specifically, I use this to mean Christian young-earth creationism; the belief that Earth was created in 6 literal days as written in Genesis 1.
Taxon: a division of life: kingdom, phylum, class, species, etc, or an example of such a division (Animals, Chordates, Mammals, Humans, etc)
Precambrian (4500-545 Mya): Primordial epoch; from the formation of Earth until the Cambrian explosion. No plants or animals.
Paleozoic (545-245 Mya): Ancient epoch; from the Cambrian explosion until the Permian extinction. Age of trilobites.
Mesozoic (245-65 Mya): Middle epoch; from the Permian extinction until the K-T (dinosaur) extinction. Age of dinosaurs.
Cenozoic (65-0 Mya): Recent epoch. Starts with the K-T extinction and continues today. Age of mammals.
Subject 1: Evolution and the Origins of Life
The most immediate question one can ask regarding origins is where humans - and, for that matter, other life forms - came from. The secular world has long since identified evolution as the theory that best answers this question. The theory of evolution is also the target of the vast majority of creationist attacks, probably because they find the idea of humans stemming from "lower" life forms particularly abhorrent. Many of the criticisms are dated or irrelevant; others are outright falsehoods. In any event, with very few exceptions they refer to the same categories of evidence as supporters of evolution do but draw different interpretations, generally using arguments that are either based on a minority of cases but are refuted by many others, based on false...