Does anybody have any information on what each civilization starts with?

well, everybody starts with a settler for one. sometimes civs start with a warrior as well, and sometimes you have a scout. I think its the expansive civs that get the scout, not sure.

I know Spain doesn't get a scout to start with. They get a warrior.

Everyone starts with a Settler.

If you select a civ that has one of its starting technologies (not trait) as hunting, then you get a scout. Otherwise you get a warrior.

If you play as the Incans, you get their unique unit.

If you play as the Incans, you get their unique unit.

True, because that unique unit replaces the warrior for the Incans.

edit: I have never played the Incans; therefore, I missed it in my earlier post. Are there any other civs with a UU that replaces a warrior?

True, because that unique unit replaces the warrior for the Incans.

edit: I have never played the Incans; therefore, I missed it in my earlier post. Are there any other civs with a UU that replaces a warrior?

no, its the only one that has a UU that replaces the warrior.

one of those custom made civs that are up for download could have a UU replacing the warrior.

for the default stuf just look in the civcivilizations.xml file and look for the civ tehn words free unit

There's a comprehensive resource here: http://www.civfanatics.com/civ4/info/civilizations/

or just look at your civ4 manual, it says right in there