Hi Guys
We recently installed the tractorcow Campaign Monitor module into SS, but found the documentation that came with it required a fair bit of knowledge of SS and required the person installing it to fill in a fair few gaps. We've developed a bit of a 'how-to' that steps through the process in a bit more detail, improves the API key/list ID settings, and comes with an example form that is generic enough to install almost as is.
EDIT: Just found sunnysideup's Campaign Monitor module: It's not as sophisticated as this one from NIcolaas Francken, in that it doesn't use the latest version of the Campaign Monitor API, and doesn't provide any hooks to Campaign Monitor other than subscribe, but it's fairly simple to install and use and contains a heap of comments to help you understand adding custom site configuration variables and using a custom form model.
If anyone's interested, let me know and I'll post it.
Pete