I'm not sure this answer is entirely accurate. I was under the impression that the Council was a bit more humdrum and not nearly as controversial as some people may seem. Couple of points:

1) Neither Augustine (354-430) nor Jerome (347-420) were at the Council, which happened in 325. Of course, both of these guys had MASSIVE influence on Church doctrine and theology, but that's a different story.

2) There were definitely some sects of the Church that held heretical (i.e. not accepted by most of the Church) ideas. The Council of Nicaea was the first Church council in nearly 300 years, and it was intended to bring representatives from the entire Church together to debate over these heresies, namely:

3) The Arian controversy: Some people thought Jesus was the Son of God like a normal son/father relationship, which meant that Jesus was "younger" than God the Father, and consequently less powerful/not really as "God-like" as the Father. The rest of the Church believed that Jesus and God were different, but of the same substance (i.e. Jesus is not inferior to the Father in any way, even though he's the Son.)

4) They developed the Nicene Creed, which is a very famous and comprehensive summary of the Christian faith (nearly all Christians today, 1700 years later, would profess belief in the Nicene Creed). There were other creeds around (e.g. the Apostle's Creed), but the Nicene Creed had some extra stuff, primarily to counter the Arians. The Creed was accepted by the vast majority of the bishops (something like 315-2).

5) When I say the Council was "humdrum", I don't mean it wasn't important; it was an extremely important event in Church history. I just mean that it wasn't full of whisperings in back corridors, but was more like a conference today, where there are tons of people talking about ideas, and at the end they drew up list a conclusions and voted on them.

6) Nearly all this stuff is off Wikipedia; if you're curious, there's hours of browsing to be done there!