Templates for confirmation letters can be found and downloaded at the Docstoc and Sample Templates websites, and samples of confirmation letters can be found on the Office Writing website. The best place to find templates depends on what kind of confirmation letter is being written.
The Docstoc website has templates uploaded both by users and by professionals, and specific types of confirmation letters can be found by searching in the Search Box. There are two downloadable templates on Sample Templates for letters confirming employment. OfficeWriting features 10 different examples of confirmation letters, as well as examples of many other kinds of business documents.