Some genius guy came up with a way to emulate project management software on Google Spreadsheets. He has a video tutorial (below) and a template. It uses the SPARKLINE function to draw charts within a single cell. So much for GanttProject, OpenProject etc., eh @matthias? 
I am already using it for making GANTT charts for European research projects. These require some change to the code, because you do not typically know ahead of time the calendar start date of the project. So, GANTT charts in EU proposals are done in relative time: the project starts at month 1 and ends, for example, at month 24. The original template thinks in calendar time, and uses the TODAY() function, so I had to change that around. My EU-research adapted template (still unfinished) is here.
