Not really focused on gaita, Paulo's pages have a good account of Galician folk (traditional and renewed) groups. The only thing for the foreigner visitor is that they have been written in Galician, but if you speak either Spanish or Portuguese, you have chances of understanding most of their contents. In any case, they have links to english-written pages as well.
The Autonomous Government of Galicia (Xunta de Galicia) has a database with addresses and contact persons of Galician bands of all types, ranging from women traditional singers (pandeireteiras) to jazz bands. It is accessible through WWW.