There are some low cost Content Management packages that allow you to change your website without going through a web designer. But, by preference, you should ensure your Web developer provides you with a simple content management tool.
For more information CMSWatch,
Wire are independent sources of information, analysis, and reports about web content management solutions while
Manager has a very comprehensive listing of CM vendors.
Also see the TechWatch
article and the other at Cultivate
- both refer to academic systems but cover the area very well.
Finally, you can download the factsheet "Content Management"
or visit the home of the "Content Management
Bible" for more help.