I've worked with a number of clients on this issue. We're unbiased on CMS platforms since we consult on best practices and strategy, so don't promote any particular one. We don't do design or implementations...that being said.
We've recommended Drupal a lot. There's also a great comparison site;
CMS Watch: Content Management, Enterprise Search, and Portal Reports with available reports and comparisons.
The first thing we do is to determine and understand the needs and wants compared to budget, such as;
- What do you want members to be able to do?
- Who is going to moderate any forums (if that is to be a feature)
- Who will act as Publisher, Editor, Writer and what will be the approval processes
- What kind of digital media will you want to allow (text, images, video, audio)
- How important is SEO?
- What are the business objectives?
- Is there a business model element (i.e. are you looking to generate revenues?)
- Who will maintain any technical issues when something breaks? Something always does.
- Is bandwidth and hosting an option?
- Do you want to use an Open Source or Closed Source solution? Budget related.
- How important is design and the UI?
- How much training is required? Ability to train and ongoing training for lost people?
Those are the essential questions we look at to help define the right solution. We have recommended Wordpress a number of times adding vBulletin as the forum sections. You can take a "Blog & Comment" approach or a more in-depth approach like this wonderful WebPro approach.
Just some thoughts.