In this site, you can upload any document (it supports many formats) in one format and after that you can download that file in many other formats like you upload a word document and you can download that file as pdf or plain text or even as mp3 file.
check out more details here.
You don't need to sign up to upload files. You can embed your documents in your site in flash player.Update: Anonymous uploads are no longer available. You must register before uploading.