First: Matthew 25:31ff: "When the son of man starts his revolution with all his band around him, then he will assume authority. And all the nations will be assembled before him, and he will sort them out, like a farmer separating his cows from his hogs, penning the cows on the right and the hogs on the left. Then the Leader of the Movement will say to those on his right, ‘Come, you pride of my Father, share in the Movement that was set up for you since creation; for I was hungry and you shared your food with me; I was thirsty and you shared your water with me; I was a stranger and you welcomed me, ragged and you clothed me, sick and you nursed me; I was in jail, and you stood by me." (Cotton Patch Version)
Second, Acts 32-35: "Now a single heart and soul was in the body of believers. Not one of them considered his property to be private, but all things were shared by them. With mighty power the apostles were giving the evidence of Jesus' aliveness, and upon them all was a spirit of abounding goodwill. You know, there wasn't a person in the group in need. For owners of land or houses were selling them and bringing the proceeds and placing them at the disposal of the apostles. Distribution was then made to everyone on the basis of his need." (CPV)
I haven't figured out why most Christians don't read these texts and immediately see that capitalism has nothing in common with the economic principles of Jesus and the first Christians.
Of course, one could call this something other than socialism. It took me years to personally feel comfortable with the word. At times, I called it communism or communalism. I never saw this as something centered in the State like the bureaucracies of Communist nations. One idea that made a lot of sense to me was a global network of church-based communes, forming a counter-economy that would grow in time to displace capitalism. I still think something like that would be very cool, even if it couldn't be socialism for everyone. After all, socialism can be diverse, with several different forms of implementation, just like capitalism.
(Note: I intend to do a series of these, tracing the evolution of my socialist thought.)