The battle of Seattle is seen as one of the defining moments in the so-called 'anti-globalization' movement in the developed world, (the defining moment for the rest IMHO would be the Zapatista uprising). It is a subject of heated, often moronic, usually misinformed (on all sides) debate.
It is so hard to debate because very basic ideas that people don't think about become disputed. For example, the media called the protests violent, but many people's definition of violence only involves damaging people, not property.
The protesters/activists/revolutionaries/all round troublemakers/whatever were varied. Some environmentalists, some anti-capitalists, some trade unionists, some just unhappy with the state of things(ists). Each had different goals, short and long term. This is a source of much criticism, however some (including myself) see it as a source of strength.
For those outside the movement, it drew attention to the WTO. It showed that our leaders are making momentous decisions without consulting their people, in secret. More importantly, it showed everyone that a large number of people were angry, and that there is resistance to global corporatism. It is said that for every person who was at Seattle, five more were radicalized (I can attest to being one).
For those who were there, it was a picture of what can come. Something which is overlooked, was the nature of the protests. The organizational structures were diverse, and very democratic. Meetings were held to decide how things were going to be done, new non-heirarchical organizational methods were experimented with. It was a way of developing new styles of management, a working representation of an alternative.
When looking at the event, one must not look for specific goals of the protesters as a whole. It should be viewed as a representation of anger at the general state of things. Many people there didn't even know much about the WTO, they just say it as a symbol of corporate power. It was not an organized, carefully planned attempt to make specific changes. It wasn't cohesive, it wasn't even 'it', for 'it' would be a singular thing.