CMS - the meat and two vege of any decent website.
In my opinion any website made today should be built on top of a decent Content Management System. Paying someone to make simple text and or image changes in your new site is just rotten - anyone who tells you different is thieving from you...
I have written my own CMS that I use to build all my websites on top of. I tailor the CMS to your specific project so you don't get erroneous features that you don't need or want cluttering the interface and over complicating everything.
At it's core the CMS is a simple MVC architecture that allows you to create, edit, delete and re-order website content and pages with ease, in-line. Generally speaking there is one edit button per page and all functionality for the page is behind that one button - simple.
Two other options that are available is to one, have a separate dashboard that all editing and administration is done from or two, another form of inline editing that provides controls right next to the area or element you wish to edit. Pretty much point and shoot. This is usually best for smaller sites.
There are also a number of excellent, free open source systems out there. The most notable being Wordpress. Some other examples are:
There is nothing wrong with using any of the above products, they all have their strengths and weaknesses but will see you right. If you do want to use one of those I can set it up and skin/theme it for you and help with content creation/support. If these great things exist, why did I write my own? There's two reasons for that:
One
I prefer to make the CMS fit the site where as most other systems you have to design and develop around the CMS. Any limitations in the CMS impact your site. With mine, I'll modify the CMS to integrate with your site perfectly.