It really depends upon what's important to you.
As far as the most Sharepoint-like solution goes, IMO Al Fresco is it (that's good to some, but bad to others... depends on what you need).
For publishing of documents, Drupal and Joomla would be a better choice, and they can be extended very well with plugins provided by their large and active communities.
If your need is tied to business process management -- such as oversight on active projects, then a product such as Active Collab would be a better fit. It's not very Sharepoint like, but many people try to build things in Sharepoint that are ready to roll in other off-the-shelf solutions.
Good luck. Have fun checking out these various solutions!