My boyfriend and I are a pair of animators who run a Youtube channel called SloMo Ref. We decided a while back to start filming animal movement references for ourselves, but we found that we have so much of it that we might as well share it with anyone else who wants to use it. It's filmed at 240 fps and we have a wide variety of animals, from fish to dogs to birds, plus the occasional video for effects animators such as water and ice.
Hopefully you can find something of use there, and feel free to let us know if there's any particular animal or effects reference you'd like to see. Who knows, we might have already filmed it and just haven't finished editing the actual video yet!