I have had some luck encouraging code review using two methods. First, I ask some folks to look at my code and comment. Often they will do so, and in turn feel more comfortable in asking me to do so. It helps to first put your ego on the line before asking others to do the same.

I should have mentioned that I've tried this approach; the standard response was "I'd love to, but I don't have time". Since the sticking point seems to be time rather than ego, I thought I'd put my time on the line instead.

I like the point about making code available with papers; my supervisor has been talking about this a lot lately (basically, his theory is that more people will cite your paper if they can easily compare their method to yours on the same platform; providing code makes that a lot more likely).