Yes, a link on the left hand side is good - but the location is different each month so it can't really be 'permanent' . And because I like to make a nice graphic to go with it, it is slightly more time consuming than just changing some text, which is why it often doesn't go up immediately.
Sometimes the left hand side is also occupied with other things, like last month an ad for the Talinn visitors bureau.
We always try to
a) Post about it in this photography forum
b) Post about it in the newsletter.
Subscribing to either of these will ensure you find out about it!
I also put up a big banner on the main photography page for the winter competition and we did actually feature this thread on the front page for at least a couple of weeks as well as the prominent mention in the newsletter of course. And then for the last week, the banner was also on the left hand side as normal.