Besides the yellow-eyed demon, what demons or spirits were associated with power surges in the show?
All of them SHOULD if they are manifesting psychic or supernatural abilities which affect the world ACTIVELY. The show has been remarkably inconsistent with its earlier established canon. I think as the show progressed they dispensed with many of the earlier setting tricks such as flickering lights to allow the stories to be faster paced.
It also seemed many of their enemies grew more powerful and more controlled in the use of their powers so there were less of the signature disruptions they might have used to identify such entities in the past.
In the beginning, anything that used its powers, was incredibly powerful or crackled with supernatural energies (electromagnetic energies by another name) disrupted electrical fields and caused fluctuations in things electric and electronic.
This disruption should also take place anytime "witchcraft" take place. A witch is a person who has the power to effect change by magical means ("witchcraft"). Since such manifestations are performing "work", they too should have some sort of EM disruption similar to the effects caused by demons, since the source of black magic (used by most evil witches) is supposedly demonic in origin.
Entities such as ghosts who exist solely as magical (electromagnetic) fields seemed to be prime candidates for affecting electrical devices since they are little more than a coherent field of electromagnetic potential. Embodied spirits/demons do not seem to have such environmental issues BECAUSE they are housed in flesh and have to exert far less energy to control a body than manifest physically.
It also made sense that Demons who (as I have been reminded) are little more than "supercharged ghosts" should also have a similar disruptive effect when manifesting in their true/smoke forms. They may also have similar effects when/if they use supernatural abilities.
We later learn some creatures have better control of their magical energies and can perform magic without any wasted (disruptive energies) being generated. Beings such as Crowley who benefit from stealth learn to dampen their energies so even when they are being actively used, he leaves no disruption and barely a trace of his psychic presence.
Angels, while incredibly magically powerful seem to be very tidy, magically speaking. This is probably due to the range and effect of their abilities; without supreme levels of control they could leave catastrophe in their wake just by existing on Earth. While they have a host of abilities, Angels are very restrained in their use of magical abilities (as a rule) and most only performed vast magical acts out of extreme necessity.
Demons like Azazel (Yellow-Eyes) who are very powerful, have few physical or magical equals, did not seem to care as much if their powers affected the mundane world and instead seemed to relish their powers affecting human toys.
Such potent displays of magic, manifestation or use of supernatural energy may be how powerful demons, angels or skilled witches can track users of such abilities. This may be why when demons or angels go on the run, they are reluctant to use their powers in fear of attracting the wrong attention...
Power fluctuations are used pretty inconsistently from what I've seen.
In theory, just about any spirit should cause power fluctuations of some level when they manifest. They also seem to cause a steep temperature drop.
As examples of the inconsistency, in the episode Ghostfacers, every manifestation resulted in distortion of the video equipment. However, in Hollywood Babylon, there was minimal distortion of the video equipment, and in fact a portable camera was used to detect the invisible ghosts.
Demons, on the other hand, seem to trigger electrical surges while manifesting, while travelling outside of a host, or only upon conscious will (for example, in Weekend at Bobby's, Crowley shuts off the TV with a gesture, yet displays no other impact on electricity even when summoned).
I would guess that under normal circumstances, all spirits generate electric surges when incorporeal. However, some individual spirits or demons can gain specific abilities due to either power and experience (e.g. Crowley), or natural tendencies (e.g. the ghosts of the actors and actresses from Hollywood Babylon have an affinity for cameras due to their careers while living).
Human hosts possibly act as a natural dampening field for the electrical surges, since we don't normally see any surges from possessed bodies or vessels.