Things change and it's hard to keep track of this sorta stuff.
But where / who do folks think some of the largest and/or most successful anarchist/syndicalist/libcom organizations are?
I hear folks talk often of the SAC, CNT, FAU, USI for syndicalists... also groups in South America, Greece of course in a way...
What are the thoughts of comrades?
You can still count with CGT
You can still count with CGT and CNT, having around 80,000 members the first and 6000 the second one. SAC is around that figure as well, while SUD-Solidaires (a base union, non anarchist) is 100,000 members. In Spain there's also Solidaridad Obrera with another 1000 members or maybe 1500. I have no clue about the size of USI's, FAU and CNT-f's right now.
I follow the progresses of latinamerica especifista (anarchist-communists) organisations. In Brasil having a coordination of 11 or 12 organisations (CAB Brasil). FAU in Uruguay; ASL (Buenos Aires) and FAR (Rosario) in Argentina; Via Libre in Colombia; Corriente Libertaria in Peru and FCL-Solidaridad in Chile. It's difficult to know their numbers as they are cadre organisations. Those are political organisations working in 'fronts'. A student front works in the student movement (for instance FEL in Chili or Acción Libertaria Estudiantil in Colombia), or a syndical front works inside unions.
In this aspect they have had the biggest progress counting with a few unions close to libertarian positions (while not anarcho syndicalists): SIMCA (council & administration workers) in Portoalegre; SUATT (taxi drivers) in Montevideo; SINTEC (building - 10,000 members), Unión Portuaria (dockers - 10,000), miners, forest workers... in Chile... And an anarchist-communist presence in other unions all around the Continent. We can consider that anarchist militants have finished their studies and are working inside unions.
Another front is about community work. Here we could talk about a few examples like Ukamau and CTL in Chile, MOB and Resistencia Popular in Brazil, FOB in Argentina... and links to some other movements in Colombia and Mexico. Here we can find a mixture between anarchist-communist and autonomous anticapitalists militants.
A quite interesting development is the spread of autonomous municipalities around latinamerica, specially in Mexico, but also in Peru, Colombia and Chile (Mapuche). They're inspired in Zapatista municipalities (they're mostly indigenous communities), and they're rebel to the State self-managing their towns as well as they're own security (with policias or guardias comunitarias). This is the prefiguration of new "Rojavas" with some links to libertarian socialist or autonomous ideas.
As for other anarchist organisations I heard about turkish DAF having 500 members. This may be an exageration, but means a big development in Turkey. Unluckily the political situation in Turkey may thwart this growth. The same with the libertarian socialist movement in Egypt. It is difficult to keep a track of non-western organisations.
To sum up I guess the 90% of anarchist movement does not belong to any organisation.