How many Spirit Guides are the source of a Spiritualist . .

. . . organization or movement?

There's Silver Birch, of course, whose channeling by Maurice Barbanell didn't result in an organization but did result in a wealth of spirit teaching.

There's Zodiac, whose channeling by Winifred Moyes resulted in the establishment of the Greater World organization.

Can you think of any others?

Hi Left Behind, you may be correct about Zodiac but the real drive behind the Greater World was the rejection, by the SNU of Arthur Conan Doyle's proposal to add the Christ Principle as an Eighth Principle. This resulted in the Christian Spiritualists splitting away and for almost all of the 1930's although split in various groupings, being a larger body than the SNU (Different now the Greater Word and Christian Spiritualism is much much smaller).

Without that Zodiac would have been part of the SNU.

Probably the most obvious one, with lodges in the UK, Aus and USA is White Eagle; Great centers for healing and retreats.

Most of the other organisations took years to form, with many false starts and break ups. The collapse of teh first National Association in the USA as a result of Victoria Woodhull's Presidency is a classic case.

I'd heard about Sir Arthur's championing of the 8th (Christ) Principal, but I hadn't known that this was the impetus behind the split within Spiritualism at this time, and the consequent founding of the Greater World. But it makes sense: the Zodiac channelings started after WW1: the GW wasn't started until, I believe, 1931.

The human capacity to dispute, revolt, split and splinter seems unlimited and occurs in every realm of activity, so I suppose we shouldn't expect Spiritualists to be any different.

I've heard of the White Eagle Lodge, and have received some of their literature.