Here comes the Linux kernel in Android and cross-compiling. I've managed to compile G++ for ARM phones (nearly every phone). If you have Intel Atom or other x86-based smartphone it's even easier. Just download a linux binary as for PC and go.
To run the apps, use Terminal Emulator. Note it runs in full-speed, cause it isn't emulating x86 - it's native ARM linux.
What can you do with this? Well, I have LightTPD webserver with PHP, cUrl, Midnight Commander and others working great. Going to compile things like MySQL, Python or even maybe X Server & some window manager like IceWM. All of these running fast like on 1GHz PC (my phone is 1GHz), cause it's native.
What do you think about it? Any ideas what to try to compile? Wanna the binaries or screenshoots? Questions/comments? Feel free to post.