I toldja!
Homebrew PSP on firmware 1.50 No longer is it just the Japanese early-adopters who can run "hello world!" on their Sony handhelds. Now the whole world with un-updated PSPs (the 1.51 and 1.52 firmwares are still to-be-broken) can enjoy Doom, e-books and emulation.
Unfortunately, the solution arrived at here isn't exactly elegant. It's a complicated setup involving external applications and TWO memory cards. Yeah, the trick to the whole thing is to pull the ol' switcheroo on your PSP. Verrrrry sneaky! (Thanks, but I'll wait until this sort of stuff can be embedded in the apps.)
Of course, none of this is kosher according to Sony. Indeed, to bust open your PSP to unlock its potential is akin to terrorism, and is most emphatically frowned upon. You don't want to be a "terrorist" do you?