The future is mobile computing and the Raspberry Pi is the start of it :)

If you would ask me today what would be some nice mobile smart phone to buy. For some mobile computing. I would rather advice to get an mobile computer in the size of a smart phone instead of just a smart phone. Especially when you can get them bargain nowadays. Why not go for a budget solution. :)

One of the first / best (keyboard > touchscreen any day) smart phone sized mobile computers is Nokia N900. Last best device ever created by Nokia. There are even people who really want an update of it:

http://neo900.org/

You can even put a specialized tuned version of PwnPhone Debian OS on it. Full of different hacker tools. For some serious pen testing:

https://www.youtube.com/watch?v=Bzg3bsP-4Eg

Or if you would really like a next generation of this hacker friendly super phone. You can go with the MeeGo (kind of Fedora based) n9. There is even a keyboard hack possible. If you are not that much into touchscreens as i am:

http://talk.maemo.org/showthread.php?t=84025

And yes, off course there are some other newer models on the way. That try to make next generation of this:

http://www.jollausers.com/2013/07/why-sailfish-is-better-as-a-modern-os-here-is-a-comparison/

Enjoy the hacking :)

edit:
Someone said that Linux is the new Amiga. No im not agree about it.
But Maemo is definately new Amiga.
Because only Maemo makes it possible. :D