Creating an article

OpenOffice 2.3 has a MediaWiki export filter, so you can use OO Writer for formatting and then export that.

generating a box of source code (e.g. to show a script or input file for a program)

Simply introduce a blank at the start of a line. To avoid interruptions of the box, empty lines must start with a blank as well. Example:

shelxc pulg<<eof
INFL  D22-ip.hkl
HREM  D22-rh.hkl
CELL 85.71 85.71 145.34  90 90 120
SPAG P6522 
MAXM 2
eof

[math]\displaystyle{ 2 = \left( \frac{\left(3+y-x\right) \times 2}{3-x} \right) }[/math]

[math]\displaystyle{ F_{hkl} = \sum_{i=1}^{N} e^{-2\pi\imath\left( h\frac{x}{a}+k\frac{y}{b}+l\frac{z}{c}\right)} }[/math]