If your primary operating system is Unix (or a Unix derivative such as Linux), then learning C makes perfect sense. Large portions of Unix itself were written in C, and it's still a popular language for building Unix tools.
Unix people tend to be fanatical about their text editors (post a message to any newsgroup about emacs versus vi and watch the bullets fly), but there are worthy IDEs available too. Naturally, most of these are open source, such as Eclipse (www.eclipse.org), KDevelop (www.kdevelop.org), and Anjuta DevStudio (http://anjuta.sourceforge.net, Figure A.11).
If Eclipse, KDevelop, and Anjuta DevStudio aren't to your ...