Userscripts.org

I think it would be cool if you could add a 'play all' button, next/prev track, etc.

That's a little harder.
For first he'd have to make the player stay on the page and play even if the page was refreshed and make the list manageable...fukou da...

actually, it does not NEED to stay on the bottom of the page while refreshing, the main problem is to not lose the playlist when doing so...

or...
make the script find all playables on the page when you want and let you choose which ones to play...

@Sigmar: there's an edit button.

It would be a good idea though.

Edit: Edit button is right above your Firefox and Windows logo.

Still don't see it...

Storing the play state across refreshes isn't necessary. All I was thinking of was

make the script find all playables on the page

+ a 'play all button'. Choosing which tracks to play might be useful if we could see metadata.

if we could see metadata

Oh, I just had an idea - if automatically finding metadata is difficult/impossible, why not let users manually input it in the link as a JSON object? {title: 'foo', artist: 'bar', album: 'baz'}.