Hmm. Initially (and still) the pettiness, snobbiness (aka holier-than-thou attitude), false demeanor of the people within the church. Growing up, we had our "Sunday faces"... the smiling happy look that tried to say that life was just great and everything was perfect. Nevermind the physical and verbal abuse going on in the home between the parents or between the parents and the children. Nevermind the tearing down of self esteem, destruction of the idea of parental concern, the suicide attempts, the runaway attempts, the violent arguments that occurred every day. As soon as we parked our car in the church parking lot, everything was magically "just peachy."
The church "family" who never stooped to help out another family within the church who had no water, no working furnace, and no washer or dryer while the father remained unemployed and the mother worked 3 jobs to try and make ends meet.
The hatred towards those who aren't Christian (or the right sort of Christian), gay, color, or social status (and if you don't think this is true in today's church, follow this link: http://www.lovegodsway.org/)
I won't even mention in detail the misquoting and warped conception of Jesus and the Bible.
The materialism within the church not just by the congregation, but the pastor as well (mentioned by Jeff K in a previous post).
The idea that the Kingdom of God exists within a church's walls and people must come to the church to partake of it.
Salvation as is taught in today's church.
Hell and the sale of "fire insurance" (as I like to call it).
I could go on for a while, but this would get redundant, and I suspect you get a general picture anyways. I'm not saying that every church is like this and that every Christian is like this. But if you walk up to someone who is outside the church and ask them how they'd stereotype the American church, I believe they'd say a lot of the same things I said.
I love people and it burns me up to see someone stating that God doesn't love this person or that person because of who they are or what they have done. I believe that Jesus came to this world to help the people... not to create a superior religion, a big beautiful church building, a bunch of mindless sheeple. He came in humility and love... something that I feel is sorely lacking in most churches (and Christian's hearts).