The Physics of Sound video takes a look at phase shifting and All Pass Filters, and as a tryout I used the 1 Pole LPF in the Audulus library as a starting point for an APF with nice resonant qualities, and then used that as a point of departure for putting together a phaser along the lines of Hordijk's Dual Phaser. He adds some nice touches such as a switch that flips the direction of half of the modulation input, or keeps half of it static while the other half moves, as well as a fader between LP and Phaser modes. I find the nicest thing is being able to push up resonance and then trigger the phaser with sub-audio pulses for some nice percussive sounds.