[cd34]

Do you use the wordpress editor? If so, there is a 'more' button in the editor which puts a break in and allows the post to continue on the second page.

Settings, Reading, For each article in a feed, show Full Text/Summary

this splits it at a hardcoded # of characters, I don't remember how many, but, it breaks on a character boundary and they back up a little so they don't split a word. It uses the excerpt if one is written, otherwise, splits the post.