How do I limit the number of images displayed in a teaser? I have a site with an image field that allows for unlimited images. I want the first image in the field to be shown in the teaser (for both listing and views). Is there a configuration option that will let me do this?

I'd rather not put in a self-written module (as it means I have to maintain it myself).
Try using this module http://drupal.org/project/field_multiple_limit

It allows you to go into the display settings for your content type and configure the teaser settings to display only a certain amount of values. You can even make it skip vales, for example if you want it to display values 2 to 5.