Should I write my own CMS?
Judging from your goals it seems like it'd be easily accomplished in Drupal with minimal work.
www.drupal.org
Forums and user blogs are built in and I'm pretty sure I saw a wiki module somewhere.
However, if you're going for a learning experience - doing it yourself will be quite the learning experience. Whether you actually accomplish it or not you will understand RoR and/or PHP better by the time you're done.
roll out your own :)
you will gain experience (which is priceless), and on top of that you will end up with something thats not bloated...
What you shall do is up to your own discretion, but what you should do is implement something like Drupal.
Drupal is a CMS which is intended to be used for community sites. It's not the easiest system to understand and use, but it's very customizable.
Here's some references that you could use to get started learning about Drupal: http://www.packtpub.com/drupal/bookhttp://drupal.org/node/367131
Whenever you have to choose between writing something for yourself and using existing software there are four key pieces of information you need to account for.
- How Complex will it be?
- How closely does an existing system match my needs?
- What would it cost to implement an existing system Vs write your own
- How soon do I need it?
If it's not very complex, nothing else really matches your needs well, it would be cheap to create (in time and money) and you don't need it immediately then go ahead and do your own thing.
Otherwise, jump on board one of the existing open source CMS's and start contributing there. Not only will you get great feedback from experienced programmers, but you'll be part of some really awesome software.