I am building a website and need to use a CMS. If I use an already made CMS, I need to be able to extend it easily. Is there a specific CMS that you recommend or should I make my own?
OpenSourceCMS is an excellent place to start. They offer demos, user rankings, etc. of many different CMS systems.
You can also find relevant questions here on stackoverflow by searching for "php cms".
Personally, I like Drupal, MODx and Concrete5. Drupal and MODx because of their extensibility, Concrete5 because of its simplicity.
Had the opportunity to use Joomla, there are many plugins/templates/tutorials and a few books out there. If you are good in php you will find it very easy to create your own plugins or extend existing functionality. However big drawbacks are the many exploits and some limitations (only mysql as a database, versioning of articles, detailed permissions, multilingual support) that hopefully will all be fixed with Joomla 1.6.
The beauty of most good packages is it won't hurt you too much to get dirty with a few of the well managed and easily installed packages to see what's best for you.
I have stumbled through Drupal and ended up on Joomla. I found Drupal to be highly powerful and technical. Joomla is the same, but seems to do straight-forward stuff a bit easier. Both work quite well.
If your application is very simple, Concrete5 is definitely worth looking at. I go with Joomla for most projects right now and am keeping a close eye on Concrete5...
Let us know what you went with and why!
its sad that no one seems to include wordpress in these discussion my recomandation is wordpress.org but it also can be wordpress MU and MU in combination with buddypress
one great advantage of wordpress is plugins it has if not the most extensive plugin selection and on top of that the same goes for its template selection please do check them out
I have found SilverStripe to be quite useful, used it on an intranet project - built in authorization, nice content editing built in, easy templating language, workflow, content versioning. I also like that they have good documentation and Help. The Demo is also impressive.
If you are looking for simplicity try Concrete5 or MODx. They are both easy to install and work with.
I really like SilverStripe's admin and extendability. Right now, I'm running http://gallery1401.com/ on SilverStripe. It has nice image upload, and custom fields, and rails-like associations and data management. Runs on a typical php/mysql stack, with strictly object-oriented architecture.
I'm surprised no one mentioned ExpressionEngine. It is not free (that's probably why) but it's PHP, has a thriving community, a lot of plugins (good ones not free, but a php programmer could consider this a possible revenue source). It's built on a PHP framework - Code Ignitor.
I'm playing with Concrete5 right now - I really love the in page editing. It's MVC based, extensible. Simpler (so far) than EE, EE is easy to use and template, simpler than Drupal. Drupal is amazingly powerful, but as others have noted there is a steep learning curve. Even if you're a php whiz you have to learn "the Drupal way" to template, to code, everything, it's really quite involved. That said, Drupal can really do anything and powers some very robust and high profile sites and has a huge community.