ZP Posts Per Page
This free ClassicPress plugin was inspired by the abandoned WordPress plugin “Custom Posts Per Page” and allows you to set custom values for the number of posts shown per page for the various archive pages. It has been built from the ground up for ClassicPress and includes all the same features, with the addition of custom taxonomies (which were not catered for in the original plugin).
You can have different values for page 1 and subsequent pages of any archive or taxonomy. So for example, you can make category archives show 5 posts on page 1 and 7 posts on page 2, page 3, page 4, etc. This is useful if you are styling page 1 differently from subsequent pages, perhaps to visually highlight the most recent post.
Leave a comment on the plugin homepage or use these forums. All feedback welcome.