I know that as a student, it can be hard to be aware of all the various competitions or science fairs that are happening, especially over a wider geographical region. I think we should help each other out, and be aware of various events that could be interesting. By keeping others in the loop about such events, we can all benefit from the greater exposure.
In the comments below, I have listed some geographical regions (International, US, India, Asia, Brazil, UK) If there are events in those regions that you think others may be interested in, please add them as a comment to the relevant region. If you do not see your region, feel free to start a comment, and then add on the events underneath it.
If you find this useful, let us know and we'd create quarterly (or even monthly) updates for your easy reference. For now, let's keep it to the end of 2013, to increase the relevance to others.