SharePoint 2010 Site Pages
Ran across this excellent blog post on SharePoint 2010 Site Pages. Hopefully's Ted Paddison's upcoming Inside Microsoft SharePoint 2010 will include as clear an explanation as this does.
Haven't had time to look yet, but the mention of Community Kit for SharePoint: Development Tools Edition looks like something worth exploring.
Here is a similar article which explain how to create a (publishing) page layout, but it has a bit more screen shots to it compared the other article.
See this article on MSDN for background on the different types of SharePoint 2010 pages.