
What is it then? Why has this genre survived for so long with attention spans getting shorter and other, more obvious genres standing out so much more clearly? Let's ask some questions...
What's it about?

Your average Psytrance song will pound a repetitive arpeggiated bassline over a 4-on-the-floor beat for a goot 7-10 minutes, with repetitive lead synths steadily building and dropping throughout. It's the reduced focus on structure and increased focus on repetition that makes it so entrancing.
As with pretty much any music, there are other aspects to the culture that accompany the audible side of things. In this case, it tends to be something to do with illicit substance abuse and hippie-esque kaleidoscopic imagery. Tie-Dye and Psytrance go together like peas in a drug-filled pod.
In the mid '80s in Goa, India, the DJs that had thoroughly rinsed their Pink Floyd Vinyls decided to move towards electronic experimentation, remixing artists like Frontline Assembly and Front 242 into looped, danceable forms.
Clubs and Festivals adapted from the old psychadelic rock style to the new electronic style, fusing the European culture with the already established hippie culture to bring about the birth of the new wave of music.
How did it start to get popular?
For many years it was purely kept to the clubs, being difficult to get hold of albums of psytrance. However, in the early '90s, the first Psytrance album was released, though at the time it was known as "Goa Trance".
The term "Psytrance" didn't come into general useage until the mid '90s, when the music had evolved into a more refined concept. By this time, many mainstream DJs had picked up on the style, playing it to its commercial death a few years later, as it faded back into relative obscurity.
It does what it's supposed to do really well - hypnotise. Listening to the stuff induces a sense of intense relaxation so effectively that people have continued making it for decades. That combination of resonance-happy filter modulation, repetitive beats and unusual lead synths has, with no small amount of assistance from illegal substances, proven a solid means of tapping into that darker side of music, without losing the intensity of danceable electronica.
Where can I get samples for it?
Primeloops samples such as "Club Bizarre" or other similar progressive house packs provide a good starting point - just remember to be a bit more repetitive with the synths! Couple that with some ambient samples such as "Ambient Illusions" and you're well on your way to becoming a Psytrance master!