What is the "right" wiki to install and use? I have experience with twiki. While I don't recommend it whole-heartedly, one should consider it seriously. Let me give various factors that you should consider to make a decision. And apply these to other wikis.

• Feature Set: Authentication, Access Control framework. Wiki is an environment that allows edits from web, and with a simplified markup, makes it easy to create and manage information. However, a typical corporate deployment will require a lot of other capabilities: Access control to pages, hierarchical webs, groups capability, and so on. You will also require authentication capabilities against sources such as LDAP servers. TWiki scores very well in all these. However, security is bit week.
  
  
• Feature Set: Plugins for Integration with other data sources: One of useful functionality of twiki framework is its capability to integrate with databases and other data sources.
  
  
• Deployment Environment.. Within an organization, you have to provision lot of users, make sure that performance characteristics are met. Security is another consideration. (And twiki has many security holes - Limiting access to a closed group.) If you are installing it with ISP, then you would typically want a CGI solution, which you could probably install in your area in the server. Twiki scores well in this aspect.
  
  
• Manageability



• Plugins


And so on. I will add to this list incrementally.