I naturally tend to associate the spectrum of psychedelia with rock, derived from the halcyon days of Hendrix, 13th Floor Elevators, Electric Prunes, Funkadelic, space rock a la Hawkwind, some prog a la Floyd or Soft Machine, etc. and into modern-day neo-psych like Of Montreal or Tame Impala. To me, a band like Ozric Tentacles is quintessential psychedelia. As it's not my primary area of music, I tend to overlook areas of, like, acid house or trance. I guess there are lines to be drawn between "psychedelia" and "psychedelic".
I like Boards of Canada, but I've never thought of applying the "psychedelic" label to them. I've always thought of them as ambient electronica.