I've registered a site where I plan to post information, pics, and personal criticism for different restaurants, venues, clubs, etc... Is it illegal to post pics of these places? Or give my personal criticism or comments about these different places or businesses?
If you took the picture in a public place, you can post the image. You can't take a photo you found and use it without permission. You are free to post your opinions or review of places you visit, just don't post anything as a fact unless you are prepared to prove that it's true. There are some limitations on what you can post as an opinion - i.e. "I think the restaurant is serving cats they found out back and telling you it is chicken".
This is tricky ground. If you are putting up the pictures (that you took yourself) for the purposes of critique, it is usually allowed, but you have to be very careful of your comments as many food critics, for example, and their newspapers have been taken to court when they have bagged a restaurant to harshly.
You may want to research libel laws. The pictures thing, your good to go as long as you take the pictures yourself (or purchase a license to use them) and take them from a place you are legally allowed to be, such as the public sidewalk.