Sample Focus - The easiest way to find the perfect audio sample
Freesound - The Freesound Project is a collaborative database of Creative Commons licensed sounds.
Sononym - Finally, a sample browser that understands audio
Userflows - Automatically generate user journeys
Sampurr - A web-based tool for sampling audio from Youtube, Vimeo, Soundcloud, and many many more.
Samplescope - Simple audio sample search