New Zealand Informatics Competition
Here are some guides you might also find useful:
A good book on competitive programming.
Sources of problems (other than our own train.nzoi.org.nz):
- US: http://train.usaco.org/usacogate
- Australia: http://orac.amt.edu.au/cgi-bin/train/hub.pl
- Croatia: http://hsin.hr/coci/
You can also find problems at these online judges:
Let us know at email@example.com if you have more resources worth sharing.