1. General sites of linguistic interest:
The Linguateca site for computational linguistics has extensive resource lists and provides direct access to a large number of corpora of modern Portuguese and Brazilian (see below)
The Portuguese Language page of Cambridge University has some useful links
The Instituto Camões site has a section dedicated to Linguistics
The best collection of corpora is available through the Linguateca site
For instructions on how to use these corpora, see my Corpus searching guide
The Centro de Linguística da Universidade Nova de Lisboa has a Corpus Informatizado do Português Medieval (with a verb dictionary and online texts: for full access you need to request a username and password)
3. History of Portuguese
The Universidade Federal do Rio Grande do Norte hosts a simple site on the History of Portuguese (mainly cribbed from standard sources)
Similar materials are found on the Instituto Camões site.
Samples of Dieter Messner's Dicionário dos dicionários portugueses are online at the University of Salzburg site.
5. Other electronic materials
The CLUL has issued a set of 4 CDs with samples of Português falado (available in the Portuguese Centre).
Stephen Parkinson, 5.11.05