Did you know he wrote "One (Is The Loneliest Number)" the song that made Three Dog Night famous? This is Three Dog Night's version, which is a classic rock staple and one of my favorite songs ever:
This is Nilsson's version. It doesn't have Three Dog Night's legendary rockin' breakdown but the smooth bass line and more subtle production makes it feel a little more soulful, a lot more sincere, and much more, well, lonely. I'm honestly torn about which "One" I like better--the feeling is extremely different.
Aimee Mann, the Dresden Dolls, the Ambitious Orchestra, and your mom have all done fantabulous covers, too, but Nilsson's and 3DN's versions are unbeatable.
And here's an amazing cover by Nilsson of "Without You" by Badfinger (the band that would have been destined to be the next Beatles had they not killed themselves to death). Not the cover of that song he's famous for--my mom's favorite song ever, and one I grew up listening to a lot--but an obscure demo that I personally find far more powerful, because it brings out the best in both Nilsson's intense delivery and his capability for restraint. Still a very sentimental song, but it blows Mariah Carey's sapfest right out of the water.
Just goes to show that as fond as I am of mashups, indie rock, all this crazy new avant-garde music, some things only get better with age.