Kid's Software.
Education is a under-developed country in the software world.
Do the research, you will find there is, relatively speaking, very very little (monetary) reward for writing educational software either here in the UK or in the US.
Although education can benefit greatly from correct application of technology, all we do is shove more hardware at them instead of coming up with better software and interfaces that widens the teaching opportunities.
Take for example, GameBoys. There are millions of these things and kids are absolutely attached to them, yet there are very few educational software for GameBoys. Even a simple software like electronic flash cards could do wonders to kids. To do this, all one needs is a GameBoy cartridge capable of running Java (i.e. JemBlazer) and a means of communication with a nearby PC like USB, Bluetooth, or even Wi-Fi. [Don Park's Daily Habit]
Oh for a pound (or dollar) for every time someone comes up with this idea. All we have to do is write education software to run on the grames machines, the games industry earns billions, all we've got to do is convince them to make it more educational. To a kid there is no value proposition here. Age of Empires is educational, but it doesn't look like it in any way at all - put any sort of "and this is educational kids" and sales would drop. IMHO, most kids don't like being "educated" - they go to school (because they have to) for that.
There has been, continues to be, a massive amount of innovation in education software by large numbers of very talented people - the rewards are poor and they go unrecognised.