Progressive rock has a very vibrant presence on the internet, with a number of communities and sites all with their particular strengths and idiosyncrasies. Over the years, I have probably visited Progressive Ears, Progarchives and DPRP more often than most, but there are many others, including sites hosted by individual bands (such as the BBT Facebook Group.)
Now, there is a fine new prog site called Progarchy which I strongly recommend. The site functions as a blog and includes reviews and articles. The number of contributors and readers is expanding very rapidly and I forecast that Progarchy will become an essential resource for prog listeners. The site can be found here and followed on Twitter here.