Gibraltar Encyclopedia of Progressive Rock - huge database of quality reviews.
Tommy's Forest of Progressive Rock - great review site!
Gnosis - Reviews and ratings (1-15) by what seems like reliable people
Progressive Ears - including a very active discussion forum.
Progressive Newsletter - in German, but they have thousands of prog links.
Italian prog - The ultimate site on Italian prog
New Horizons - reviews, interviews, news and more.
Progreviews.com - Loads of quality reviews.
Zoltan's Progressive Rock Webpage - reviews and sound clips.
Frazz recommends... - Italian prog reviews
Google Groups - Discussions about prog on rec.music.progressive
Record Heaven - Online vendor from Sweden.
Manlio Progressive Reviews - Reviews in Italian.
Raimundo Rodulfo - Latin American prog artist, nice sound clips.