There aren't enough of these, actually. Every new web app seems to be in the SaaS model. Frankly where I'm at is too small to justify the spend (our content team uses and loves Basecamp but our three-person dev team absolutely hates it). We just want something to run internally within our team.
All of the open-source tools are quite old and a pain to set up.
In the end, I want an open-source tool with a focus on easy customization with plugins and custom solutions through code itself.