The Spanish Revolution of 1936 began during the outbreak of the Spanish Civil War. Much of Spain's economy was put under worker control; in anarchist strongholds like Catalonia, the figure was as high as 75%, but lower in areas with heavy Communist influence. Factories were run through worker committees, agrarian areas became collectivized and run as libertarian communes. It has been estimated by Sam Dolgoff, author of The Anarchist Collectives: Workers' Self-Management in the Spanish Revolution, that over 10 million people participated directly or at least indirectly in the Spanish Revolution. Even places like hotels, barber shops, and restaurants were collectivized and managed by their workers. George Orwell describes a scene in Aragon during this time period in his book Homage to Catalonia. 
"I had dropped more or less by chance into the only community of any size in Western Europe where political consciousness and disbelief in capitalism were more normal than their opposites. Up here in Aragon one was among tens of thousands of people, mainly though not entirely of working-class origin, all living at the same level and mingling on terms of equality. In theory it was perfect equality, and even in practice it was not far from it. There is a sense in which it would be true to say that one was experiencing a foretaste of Socialism, by which I mean that the prevailing mental atmosphere was that of Socialism. Many of the normal motives of civilized life--snobbishness, money-grubbing, fear of the boss, etc.--had simply ceased to exist. The ordinary class-division of society had disappeared to an extent that is almost unthinkable in the money-tainted air of England; there was no one there except the peasants and ourselves, and no one owned anyone else as his master."
Continuing, Orwell describes the general feel of the new society that was built within the shell of the old:
"This was in late December 1936, less than seven months ago as I write, and yet it is a period that has already receded into enormous distance. Later events have obliterated it much more completely than they have obliterated 1935, or 1905, for that matter. I had come to Spain with some notion of writing newspaper articles, but I had joined the militia almost immediately, because at that time and in that atmosphere it seemed the only conceivable thing to do. The Anarchists were still in virtual control of Catalonia and the revolution was still in full swing. To anyone who had been there since the beginning it probably seemed even in December or January that the revolutionary period was ending; but when one came straight from England the aspect of Barcelona was something startling and overwhelming. It was the first time that I had ever been in a town where the working class was in the saddle. Practically every building of any size had been seized by the workers and was draped with red flags and with the red and black flag of the Anarchists; every wall was scrawled with the hammer and sickle and with the initials of the revolutionary parties; almost every church had been gutted and its images burnt. Churches here and there were being systematically demolished by gangs of workman. Every shop and cafe had an inscription saying that it had been collectivized; even the bootblacks had been collectivized and their boxes painted red and black. Waiters and shop-walkers looked you in the face and treated you as an equal. Servile and even ceremonial forms of speech had temporarily disappeared. Nobody said 'Senor' or 'Don' or even 'Ústed'; everyone called everyone else 'Comrade' or 'Thou', and said 'Salud!' instead of 'Buenos días'. Tipping had been forbidden by law since the time of Primo de Rivera; almost my first experience was receiving a lecture from a hotel manager for trying to tip a lift-boy. There were no private motor-cars, they had all been commandeered, and the trams and taxis and much of the other transport were painted red and black. The revolutionary posters were everywhere, flaming from the walls in clean reds and blues that made the few remaining advertisements look like daubs of mud. Down the Ramblas, the wide central artery of the town where crowds of people streamed constantly to and fro, the loud-speakers were bellowing revolutionary songs all day and far into the night. And it was the aspect of the crowds that was the queerest thing of all. In outward appearance it was a town in which the wealthy classes had practically ceased to exist. Except for a small number of women and foreigners there were no 'well-dressed' people at all. Practically everyone wore rough working-class clothes, or blue overalls or some variant of militia uniform. All this was queer and moving. There was much in this that I did not understand, in some ways I did not even like it, but I recognized it immediately as a state of affairs worth fighting for."
The communes were run according to the basic principle of "From each according to his ability, to each according to his need". In some places, money was entirely eliminated, to be replaced with vouchers; however, in practice these "vouchers" performed and functioned as money themselves.
Despite the critics clamoring for "maximum efficiency" rather than revolutionary methods, anarchic communes often produced more than before the collectivization. The newly liberated zones worked on entirely libertarian principles; decisions were made through councils of ordinary citizens without any sort of bureaucracy (it should be noted that the CNT-FAI leadership was at this time not nearly as radical as the rank and file members responsible for these sweeping changes).
In addition to the economic revolution, there was a spirit of cultural revolution. Traditions some viewed as oppressive were done away with. For instance, women were allowed to have abortions, and the idea of "free love" became popular. In many ways, this spirit of cultural liberation prefigured that of the "New Left" movements of the 1960s.
As the war dragged on, the spirit of the revolution's early days flagged. In part, this was due to the policies of the Communist Party of Spain, which took its cues from the foreign ministry of Stalin's Soviet Union, the source of most of the foreign aid received by the Republican side. The Communist policy was that the war was not the time for the revolution, that until victory in the war was won the goal had to be the defeat of the Franco forces, not the abolition of capitalism, which was to be addressed once the war had been won. The other left-wing parties, particularly the anarchists and POUM, disagreed vehemently with this; to them the war and the revolution were one and the same. Militias of parties and groups which had spoken out too vociferously in opposition to the Soviet position on the war soon found further aid to have been cut off. Partially because of this, the situation in most Republican-held areas slowly began to revert largely to its prewar conditions; in many ways the "revolution" was over well before the triumph of the Franco forces in early 1939.