This module just comes so handy. Instead of reading tons of RFCs and embedding images into built emails yourself (fetching, encoding, linking the part-id ...) you can simply throw some HTML at it. The only feature I had to add myself was to make the resolver not die if an image couldn't be found.
But this is the module I use in every project that has to send HTML emails with embedded images and since a few years it did a very good job.
Finally! A replacement for the buggy, poorly constructed MIME::Lite::HTML. When your people now say, "We made a web page and we want to email it to people," you can very very easily do this without having to think about it. It takes care of all the annoying rewriting and attaching for you.