TwentyTen-Changing Number of Posts per Page

Hey, hoping someone can help with the seemingly basic question (but one I’m struggling to answer!).

Using the TwentyTen theme, I’d like to display different numbers of posts on different types of pages. For example, one post only on the main page and 10, say, on the category-archive and search pages.

Right now, the reading setting changes the number across the board.

Thanks in advance for the help!

Matthew