Mark Roberts has a very insightful post series: Cultural Impact or Cultural Irrelevance: A Christian Dilemma. I'm not sure he's said anything I haven't seen or thought before (except his particular focus on seeing some of what I've seen elsewhere in Philippians, the details of which I was unaware of in the passages he cites), but he seems to me to have a rare combination of maturity, balance, forthrightness, and understanding of the culture around us. It's nice to see it all encapsulated in a short place. Highlights:
"Most of the people who shape our culture, especially those who produce television shows, movies, Broadyway [sic] plays, rock music, and MTV videos, live in a moral universe that's far different from the moral universe of Christianity. Their perceptions of right and wrong differ vastly from the perceptions held by most Christians. This isn't a gripe. It's simply a fact."
"Those in the Christ against Culture camp recognize that culture opposes basic Christian values. Therefore they tend to withdraw from the world, either trying their best to ignore it (the Amish option) or taking pot shots at the world from a safe moral distance. Separation from the fallen world is, at any rate, central to Christian living."
"The Christ of Culture folk are much more accepting of culture. Opposing the theological conservatism of the Christ against Culture camp, they espouse a liberal theology that allows culture to determine the shape of Christian living. So, if the culture blesses sex outside of marriage, then Christians shouldn't attack this viewpoint, but rather reinterpret it in a Christian way. We should encourage fornicators to have mature, loving, just relationships, not to abandon their fornication."
"Ironically, both choices end up with a similar result: we give up our ability to impact the culture for good. Yet trying to live somewhere in the middle, to engage in a critical dialogue between Christ and culture, is tricky, not to mention messy."