The one complain I have about OpenOffice is its math presentation. Compared to LaTeX or Mathtype, it does not look very nice. Here comes the rescue: http://ooolatex.sourceforge.net/
Geany is a tiny IDE for C/C++. It is convenient to use in cases when one needs to develop short single-file programs like the ones presented in the book "Simulating Ecological and Evolutionary Systems in C".