Free online file conversion

Useful site with various free opportunities.
You can convert audio/visual/document formats to other formats. I haven't tried this but it seems you email it and it comes back to you.
No mention of what size files are accepted but, in general, you're limited to 20 MB files i a mail attachment even in Gmail.
It also allows you to send files to others. Not sure how this works but they may just mail a download url to your intended recipient.