Our pals over at Pleonasm have done future anthropologists and historians (not to mention weird-ologists of all stripes) the great service of collecting hours worth of audio oddities that mainly seem to have been recorded off of that most democratic of mediums, YouTube. There are four volumes (so far) of free downloads, organized by theme.
Vol. 1 Tongues - Largely spoken-word babbling and acapella singing, from Christians filled with the Spirit, to space-alien prophets, to drunks caught on camera, to a very funny bit of acoustic heavy metal. Tho there's plenty of unaccompanied vocals just dying to be sampled (check track #6), there's also some smooth-jazz, and blues w/ Peruvian Pan Flute. The Talking Heads named one of their albums "Speaking in Tongues," but another of their titles could apply here: "Stop Making Sense."
Vol. 2 Left Fieldists - Outsider music bonanza! Featuring such hits as: "You Tube Guy Sings About Prostitute," "Developmentally Disabled Guy Sings In Stairwell," "Song About Drinking Robitussin," "Down Syndrome Poetry," and an Asperger's Syndrome guy singing about his "Asperger's Girl." It's not all laffs, tho: "Man Sings About Infidelity" is a cringe-worthy confessional, and the "Song For My Deceased Wife" is pretty heart-wrenching.
Vol. 3 Extra Credit Songs - You can get school credit for performing music?! Damn, kids got it too easy nowadays! I would have loved that. There's a wide range of skills here, from inept singing or rapping American history or science lessons over karaoke backing tracks, to pretty professional-sounding original songs. The hip-hop/r'n'b (complete with Autotune!) "Digestion Song" is hysterical. A+.
Vol. 4 Antediluvian Moderns - Apparently an assortment of old folks. Haven't heard this one yet.