Movie Reviews

Very often professional movie critics have very different opinions from the general public. That's why IMDb is a great source to see movie reviews and ratings because you can see what hundreds if not thousands of people think of a movie, instead of just one or two critics. For instance, Juno got an average 8.2 stars out of 10 by 58,000 voters, and you can even see the gender and age breakdowns for the votes.
You also won't have a hard time finding what you're looking for: IMDb consists of the largest accumulation of data about films, television programs, video games and other media.
Product Reviews

It's hard to find trusted product reviews on the internet. ConsumerReports requires a costly subscription fee, Epinions.com is unreliable because they pay people to write reviews, and retail sites seem to have 5 star ratings for everything because they want to sell you something.
That's why Buzzillions.com is the most reliable and trustworthy product review site out there - they gather thousands of reviews a day from their 1000+ store fronts including Staples.com, Overstock.com, RadioShack.com, etc., and they show which reviews have been written by Verified Buyers - buyers who have been verified through the retailer to have actually purchased the product. Since the majority of the reviews are written by these Verified Buyers, you can feel assured that the products honestly reviewed.
Local Service and Restaurant Reviews

Ever been caught with an expensive dinner with crappy food, a mechanic that over charges, or a really bad haircut? Yelp is THE site to see what others are saying and how they're rating local services - everything from salons to dentists and doctors to restaurants and shopping. It's also a great way to find great hole-in-the-wall food places you never would have known about otherwise.
New and Used Car Reviews

Edmunds is by far the best site to read new and used car reviews. Buying a car (especially used) can be a really frustrating experience, and Edmunds is great for finding the true transaction price and ownership costs. Edmunds cuts through the chase and offers great reviews and valuable tips on both buying and selling cars. For instance, it tells you how the Kelly Blue Book was originally developed by a car dealer and can lose you a lot of money.
You can also search by zip code to find extensive information specifically for your geographic area. For example, when you've decided on a car to look at, they make it easy for you to request price quotes from car dealers in your area.
Videogame Reviews

Gamespot has been around for 11 years, and attracts some 2 million gamers per day. They have expert and community reviews on every console and pretty much any game you're looking for.
Music Reviews

Allmusic claims to be the most comprehensive music reference source on the planet, having a vast wealth of music information on even some of the most obscure albums and artists. You can find everything from old and obscure to popular and new, and read editorial reviews and in depth details from pretty much every genre of music.
They have an editorial staff as well as hundreds of expert contributors so you can find what you're looking for as well as great recommendations.
TV Show Reviews

While Metacritic has a wide range of reviews on games, books, and other categories, I see them as most useful and valid for their TV reviews. Why waste time trying to get into a TV show if everyone says it's not worth it? On Metacritic you can search for TV shows by season, see the "Best Of" rankings by year, and see ratings for upcoming TV show premiers. You can also see reviews by both critics and by viewers.