Interesting little app that came out recently is Web Audio Player. It’s just a web browser wrapped in an AUv3. It can only play certain sound sources (I guess it works by hooking into the page and detecting any audio elements, so it’s not going to work on everything), but it means you can load up e.g. Soundcloud or Freesound and play audio directly into AUM/whatever.
Was using it last night to send audio into Koala which was running in Slideover mode over the top of AUM, was a fun way to get samples in there really quickly! You can also import screen recording videos into Koala and extract the audio if you want to sample something this can’t handle