I think OpenProj is pretty good for small projects as someone pointed out.
Has anyone tried taskjugglar ?? It is available in Ubuntu repository too and it has the latest stable version.
Here is the site for the app and user manual :
Here is wiki :
It has a learning curve but thankfully, they gave a manual on their site (ignore first 25 pages or so).
Most important "milestone" is getting started with taskjugglar. However, once you get started, it does act as a true management aid for you. As opposed to other products, which are cakewalk to begin with, slowly become cumbersome as the projects moves forward in real life.
Taskjuglar is not a product to "document" your plan, but helps you make the plan after you give its basic input like tasks, estimated man-days etc. It fulfils moderm requirements like global time zone support and is also better suited for agile style management. Despite that, its still very conventional and rock solid. Its scalable. Earlier it was KDE only but now good for all unix/Linux thanks to Ruby
I am amazed that I took long time to discover it (google crawlers??) and am not surprised that none mentioned about it here too.
However, as I said there is a learning curve at the beginning but its not much difficult. It really is a management aid rather than a documentation tool for your plan.
No worries, it does churn out Gantts/PERTS's and few others too. Its not perfect though, but if it suits your need, then its a candidate for MS project replacement. for free as in $$ and liberty