Irish Republicanism and Ulster Loyalism have a long history in Ireland, interwoven into politics, culture and identity both north and south of the border. The purpose of this chapter is to highlight some of the uses of the Internet by Irish Republican and Ulster Loyalist movements over the last decade, in particular to provide some comparison between the use of the Internet by these predominantly regionally based movements, and to suggest why these differences exist in relation to the current social and political situation in Northern Ireland. The concepts of ‘communities of practice’ (Wenger, Communities of Practice: Learning, Meaning and Identity. Cambridge University Press, Cambridge, 1998) and voluntary associations (Kerri, Journal of Voluntary Action Research, 1, 43–51, 1972) will be used to frame understandings of online engagement of Irish Republicans and Ulster Loyalists respectively.