Feminism can be defined as the belief of the political, social, and economic equality of women. Although not all feminists would believe that last statement is adequate or appropriate, for some consider that "equality" forces women to complete within rules defined by men, suitable to the life experiences of men.
You can find many bloggers on feminism through the regular carnival of feminists, and at Blogher, the "community for women who blog" (which also holds an annual conference). An excellent source on UK feminism is The F-Word, and in the US check out Feministe.
There are many types of feminism, including liberal feminism, radical feminism, separatist feminism, ecofeminism, and even hip hop feminism, to name just a few.