Display: any old TV or monitor. Power: micro-USB standardized GSMA Universal Charging Solution. Keyboard and mouse: via USB port. (You'd be surprised at how prevalent TVs and cellphones are in less deveoped parts of the world.) Granted, you can't use the Raspberry Pi away from the power grid, but I would surmise that in areas were there is no electrification, there aren't many teachers or schools, so you can't really make use of the OLPC, either.

The OLPC hardware is too expensive. Even middle-income countries like El Salvador and Honduras have struggled to get them introduced into schools. The Raspberry Pi project ("An ARM GNU/Linux box for $25" - http://www.raspberrypi.org/) might just obsolete OLPC.