In a new project he's called 'Flume Sound Files', Flume has been the biggest GC and shared a dozen sound clips for free for producers to use and create music with.
The clips range between 6 seconds and 63 seconds, each with varying BPM.
There's a catch though - included in the Dropbox is a user agreement that lays out the rules for using these sounds. Most importantly, you cannot monetize anything you create from these sounds; and related, Flume can use anything you create and upload only if it is to "promote or otherwise recap" the experiment. Apart from that, the world is your oyster.
If you're keen to get amongst, you can grab all the sounds here — you can listen to a preview of each and download them. Be sure to read the User Agreement carefully though.