Valledalle from the German PSP community PSPSource.de released the homebrew game "PSP Tower Defense", which is a clone of the popular game Tower Defense. This isn't the PSP Tower Defense we have seen at the NeoFlash coding competition, this Tower Defense was an entry for the PSPSource Summer Coding Competition 2007.
The game is coded in LUA and it contains many features the real Tower Defense has, like different types of enemys, different towers and tower upgrades. And don't worry, the game is in English. You can find more information about the controls in the game menu.