This article is from the rec.music.reviews FAQ, by Al Crawford (firstname.lastname@example.org) with numerous contributions by others.
The main archive site for old reviews is ftp.uwp.edu. Reviews can be
found in the appropriate /pub/music/reviews/a-z directories. This site
is generally very busy, so please try to connect at off-peak times.
There are also other "private" archives around, maintained by the
reviewers themselves. A short list of those that I know about follows.
If you contribute reviews to rec.music.reviews and archive them, please
let me know and I'll add you to the list.
Charles Isbell's Hip Hop Resources
Glenn McDonald's The War Against Silence
Ram Samudrala's Reviews
Michael Zwirn's Kibbutz Music Reviews
Al's Review Archive
There's also an excellent index of Internet music review resources on
Yahoo at http://www.yahoo.com/Entertainment/Music/Reviews.