When designing a website you want people to be able ti find the information they need without too much effort, such as your contact number, e-mail, etc. Many places put this information in the footer, sidebar and Contact Us page. But is this information overload or simply making it hard to miss?

I don't think it's too much. A contact page is good as it provides a full choice of contact methods, it's a focal point for contacting you and lets you provide extra information such as business hours. In addition to that it's nice to have that info available on every page and easily accessible. Maybe not sidebar and footer, one or the other is enough, but it depends on what your design has room for.

If it's a commercial site I think it's good to show high levels of contactability, and that you really welcome contact with customers or potential customers. There are too many sites / companies that like to hide that kind of information away or even not give it at all.

I prefer to just use a contact page on my sites which has various forms of contact. If I was pushing a free phone support or sales number then I might have it on the home page in larger writing so people know they can call.

A contact us page is a good place to put this information in. You need to give the user different ways to communicate with you, after all that is the point of having a website, two way communication.