When it comes to China and the state of human rights in that country, a boycott is one peaceful option to convince the Chinese government to make changes. A boycott of products, goods and services made in China would send a very clear message, however it would require an effort from people all over the world. It could be a mixed bag though, as the process would cause financial harm to the very people the boycott is meant to help, by putting many of the laborers in China out of work.
Boycotting the 2008 Olympics is not an effective deterrent to prevent the Chinese government from continuing its historical tradition of human rights abuse. The government in power will continue to engage in human rights abuses as a means of retaining power as long as it is allowed to do so. Until the people overcome the government, the goverment will continue its abuses, and a simple boycott will not stop the government.