I recently ran across this interesting project on Kickstarter for Yaba. Not sure of Yaba is an acronym, but it could stand for Yet Another Brilliant Amp! Yaba is a tiny amplified speaker from PLX Devices. It's about the size of a mouse, shaped like a miniature speaker phone that you might see in a typical office conference room. You can place the Yaba on a table, floor or other flat surface to create what appears to be a pretty significant amount of sound from a portable MP3 player, iPhone or other music player. More importantly, the Yaba X version can amplify a guitar.
Of course, I wouldn't expect the Yaba X to be very loud, but if you need a way to amplify an electric guitar in lieue of a headphone amp, it might be worth looking into. There's just under 2 weeks to get in on the Yaba action for as little as $29 er $39 make that $49 or $59. The project is fully funded already, but this is a good way to get the Yaba or Yaba X before it hits retail at higher prices.