I like 
Hi-Def Digest for hi-def reviews.  They review so much there, it's hard to find something 
not in their database.
For DVDs, I've also been partial to 
DVD Movie Guide.  Again, they has a HUGE collection of reviews.  And they go into great detail on the bonus materials.  Even down to listing the running time and counting the number of pictures in photo galleries.
But the best site for reviews is 
DVD Basen.  They're not actually a review site, but a database of reviews.  You enter the movie you're looking for and they'll give you a list of every review site that has reviewed that movie.  Both SD and HD.