As Tony said, www.hometheaterhifi.com is far and away the best for DVD players and anything Stacey Spears writes there is worth reading. Their other reviews are a mixed bag.

www.cnet.com has actually become pretty good at reviewing the low end and mid-fi gear. They used to be terrible but the reviews I've read recently seem credible.

For higher end gear you can read the archives at www.guidetohometheater.com.

There are also the consumer review sites like www.audioreview.com and www.epinions.com. Some of the reviews are helpful and some are useless. The challenge is to figure out which people know what they are talking about.

Although they don't have a lot of home theater gear, www.consumersearch.com is a worthwhile site. They attempt to intelligently collate and summarize all of the professional and consumer reviews they can find for a topic.

-Dylan