I've started converting some of my favorite riffs into ringtones.
They are available for download on this page.

George Thorogood

Intro riff from "I Drink Alone"
Listen — Download

Frank Zappa

Ike Willis sayin "speak to me! Whoa nooo" in the song "Sy Borg"
Listen — Download

Ike Willis sayin "wft gwine on here" during the song "Porn Wars"
Listen — Download

Frank Zappa sayin "3 holes, no waiting" on "Little Rubber Girl"
Listen — Download

Slayer

Guitar riff from "Raining Blood"
Listen — Download

Jeff Beck

Guitar riff from "Roy's Toy"
Listen — Download

Guitar intro from "Dirty Mind"
Listen — Download

Another segment from "Dirty Mind"
Listen — Download

Cookie Crotch Nuts

Keyboard intro from "Scrodisious"
Listen — Download

Insane Clown Posse

Fockoof! cut from the "Chilito skit" - Great text notification for Juggalos.
Listen — Download

Scratching segment from "Cemetary Girl"
Listen — Download

Dweezil Zappa

Guitar intro from "Leviathan"
Listen — Download

Eddie VanHalen

Guitar tapping segment from "Eruption"
Listen — Download

Hopsin

Vocal intro from "Break It Down"
Listen — Download

Boondox

Intro segment from "Red Mist"
Listen — Download

M.O.D.

Segment from "Mr. Oofus"
Listen — Download