When Jesus called his disciples, he told them "Follow me." Given that he was physically present, there was an immediate and obvious sense to that command that his disciples would have had no problem understanding: Go where he goes, listen to him, see what his priorities are, and make them your own. What exactly does it mean for believers today?
Seeking justice for the weak, caring for orphans and widows, opposing the proud, serving the meek and lowly, and so on, are all major parts of gospel, much moreso than they are given credit for in today's evangelical churches. Jesus indicates that the Samaritan of the parable has eternal life because of things like caring for the wounded man on the road to Jericho; he warns that even religious people who do not clothe the naked, feed the hungry, visit the sick and imprisoned, and so on will be cast into the darkness, and so on.
The major mistake of the social gospel of the early 20th century was that it stressed the moral duties of a Christian, sometimes to the exclusion of the faith's supernatural aspect, reducing Christianity to a system of ethics. On the other hand, one of the major failings of evangelical/fundamentalist/Pentecostal thinking of the last century or so has been its Gnostic emphasis on saving people's souls and placing too little regard on more earthly matters like those listed above.
The failing of the much-maligned social gospel, at least as I see it, is that it comes across as an ethical or moral system of values, rather than as a relationship with people; i.e., it becomes a condescending sort of piety based on what we do to help "those poor people" rather than the true gospel of Christ, which sees other people -- even "sinners" -- as Christ, and exalts the weak and lowly as people we can learn great things from, like when Jesus upholds the poor woman who offered two copper coins as an example of generosity, commends a professional killer and various lepers for their faith, compares a socially outcast shepherd to God himself, and so on.
The big thing in evangelical and Pentecostal circles is the "personal relationship" with Jesus. Perhaps I'm being difficult, but what exactly is a "personal relationship" with God like? God never writes, he never calls, and he never sends me flowers. For all I know, he's seeing someone else on the side, broken off our relationship, and decided we're through.
I'm supposed to see him as some sort of role model for relationships, but the truth is that I hear more regularly from my younger brother in Indiana than I hear from God. My brother at least makes the effort to call me once a month or so, or to send me weird e-mails that only he and I think are funny. The whole idea of a "personal relationship" with God is something that doesn't really make sense to me, at least as I understand the concept of a relationship. At times I'm sure the application of that concept in the Western church has become downright chummy if not irreverent in the way its abandoned any sort of reverence and awe for the Almighty.