I'm giving a lecture this week in my development class (Small World: Poverty and Development on a Shrinking Planet) on multiple equilibria. We're using Todaro and Smith, and the lecture is intended to provide an alternative approach to the material in Ch. 4 of that book. Of course, I've been waving the flag of multiple equilibria, especially those arising from interaction effects, for over 30 years. (My original paper on the topic was written in – gasp – 1982.)
For the pptx version, click here. For the slightly less jaw-dropping pdf, try this.