I'll have a blog entry about it soon, but before then, you get to hear about it first: A full transfer of the USC Cinema sound effects library, which includes the work of Sunset Editorial and their hundreds of sound effects.

You can browse the collection here:

https://archive.org/details/usc-sound-effect-archive

Internet Archive: Digital Library of Free & Borrowable Books, Movies, Music & Wayback Machine

"Just give it all to me at once" types will appreciate this URL where you can torrent or download the 20gb+ of original .WAV files and metadata:

https://archive.org/details/sound-effect-libraries-red-gold-sunset-editorial

Sound Effect Libraries (Red, Gold, Sunset Editorial) : Various : Free Download, Borrow, and Streaming : Internet Archive

From the original Blog Post:The “SSE” sound effects come from the Sunset Editorial collection which was donated to USC Cinema in 1990. Sunset Editorial had...

Internet Archive

And for the real sound nerds, there's even the recording of the original Wilhelm Scream, including the sound engineers getting the actor to try different sounds before hitting the famous one:

https://archive.org/details/SSE_Library_VOICES/SCREAM/VOXScrm_Man+eaten+by+alligator%3B+screams+%5BWilhelm_CS_USC.wav

SSE Library: VOICES : Free Download, Borrow, and Streaming : Internet Archive

Sound effects from the USC Cinema and/or the Sunset Editorial Collection: ALIEN/VOXAlien_Goofy aliens or gnomes or small animals...

Internet Archive