http://www.portoeditora.com - A self-proclaimed "Biblioteca Virtual", Portoeditora does have an excellent selection of online dictionaries and other resources, as well as access to software related to Portuguese Studies.
http://www.flip.pt - This website is home to the company Priberam Informática, which produces the FLIP brand ofspellcheck software in Portuguese. In addition, the site boasts an "online spellchecker".
http://penclube.no.sapo.pt/- The official website of the P.E.N. (Poets, Essayists, Novelists) Clube Português, which offers a wealth of resources and activities pertaining to Portuguese poetry and literature.