An online directory listing Irish non-profit organisations that use the Internet. Scroll down and have a look at the full range of categories, from animal welfare to world development. An excellent reference point.
Provides information on international work camps, Asia/Africa/Latin America exchange programmes and various volunteering projects abroad. A good introduction to the wide range of opportunities available, although the website appears not to have been updated very recently.
An excellent website about volunteering in Ireland, providing a selection from the hundreds of opportunities. You can register with the placement service. Additional information includes residential opportunities and volunteering abroad.