You have probably already heard of Gimp or Inkscape as decent open-source alternatives to Photoshop or Illustrator. Scribus is a little less known, but it is growing as one of the best desktop publishing alternatives to InDesign.
Unfortunatly, Scribus can not yet compare with its Adobe counterpart in terms of functionalities, but the software has made tremendous progress with this last release. You can now use it for professional work, which was a bit risky in the past. Some of the most notable recent features are.
New drawing shapes have been added, there is even a very cool calligraphic pen available.
One of the features that has been requested the most is finally there, so you can at last add some drop shadow effects in Scribus.
Scribus now has an impressive list of formats it can import files from, so if you want to make the switch it has become a bit easier.
A simple feature that makes image management much easier in this new version.
And much more…
There are many more features, like improved PDF exportation (with PDF x/4 support) or improved typography and tables. You can see the entire list of features on this page.
The only drawback is that the software has a quite slow release rate and the next version (1.6) is only planned for April 2016, so you’ll have to wait almost a year to get new features. Meanwhile, I think you should really give it a try, a bigger user base and more feedback can only encourage the developers and push them to professionalize it.