Jira may be extremely sluggish and require a large amount of memory on the client side.
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
TiddlyWiki - a non-linear personal web notebook
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Confluence - Confluence is content collaboration software that changes how modern teams work
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.