protection from off-site links

check out [login to view URL] it's hosted with dreamhost.com. some file links are on my domain, and others are hosted on amazon S3. if possible, i'd like to ensure neither can be linked to from anywhere but [login to view URL] (and, if possible, domains i specify). i'd like a solution that provides for easy adaptation when new links are added. can javascript be used to generate timed links? if it's affordable, i might be interested in an additional automated "email the download link to visitors-" style solution too. i'm open to suggestions. thanks! ## Deliverables the email solution is totally optional.