Got free hosting, don't know what to do.

Interesting work, I think a soundcloud downloader would be good!

Have you looked at maybe coding a URL Shortener or a Bulletproof File Hosting site?

There is already too much url shortener script you can modify. I think a bulletproof file hosting site is depend on hosting and domain provider. Check this site (that carousel tho XD), look like a bs and also fishy as fuck. IMO there is no "real bulletproof". (I assume bulletproof for illegal file sharing).

Have you looked at YouTube converters?

On my to do list :D

Cool, Let me know how you get on, If you are interested in working on a project together hit me up.