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Does the power need to be supplied via the micro USB port or can one of the two normal USB ports be used as well? I intend to use SSH only, so the USB port would not be used in any other way, but I'd prefer to have all plugs on one side.

(Model B Rev.2 if it's relevant)

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No you cannot power the Raspberry Pi using its USB ports. The micro usb is the only way to power the RPi, apart from some other hacks I've seen involving solder (read the update).

Although it's not completely impossible, but you'd have to modify the RPi quite a bit to get that right. Please have a look to the Model B Rev 2.0 schematics.

UPDATE: As commented you can power the RPi using the GPIO pins and the USB (called back powering). I'm including the links, but credit goes to the commenter's.

UPDATE 2: As other Stackoverflow posts state, the new Pi's can only be backpowered once they have booted. IE: You cannot backpower the pi and boot it, the polyfuse will trip while booting.

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    This is most likely incorrect, e.g. this answer, this question and this thread suggest you can at least use the GPIO, which does not require any solder or other RPi mod. Anyway, I am aware that the micro USB port doesn't have a data connection, what's the relevance to my question though? I am asking whether I can (mis)use the non-micro USB ports as power inputs, so data transfer is irrelevant
    – Tobias Kienzler
    Commented Dec 18, 2012 at 13:20
  • I found a relevant wiki entry now, the power connectors of all USB ports are directly connected (at least with recent revisions)
    – Tobias Kienzler
    Commented Dec 18, 2012 at 13:35
  • @Morgan Does your edit mean you agree it can't be done or is it just supportive? I'm no expert in electronics, but there's only one part between the Micro-USB's pin and the +5V (which is directly connected to both the other USB ports and the respective GPIO pin), and that part seems to be a fuse, right? So assuming I use a reliable power source, should I be fine?
    – Tobias Kienzler
    Commented Dec 19, 2012 at 8:09
  • I was aware of the using the GPIO pins. I was not aware of the back powering. Have updated my original answer.
    – Vincent P
    Commented Dec 19, 2012 at 10:13
  • Thanks, now I can accept your answer. So is that part between the micro USB pin and +5V just a fuse?
    – Tobias Kienzler
    Commented Dec 19, 2012 at 11:18
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The Raspberry Pi Wiki entry on power suggests this is possible (emphasis mine):

Back-Powering; (powering the Raspberry Pi from a USB hub through the uplink/data port, single cable) Back powering is possible on the Raspberry Pi. Revision 1.0 boards have to be modified to back power, this is due to the 140ma "polyfuses" that are installed in the USB port circuit. Revision 1.1 boards do not need modifications to back-power, they have replaced the polyfuses with 0ohm resistors in their place. Revision 2.0 boards do not need modification, they have neither resistors nor polyfuses. It is advised that short (12" (.3 meter) or less) USB cables be used for back-powering a Raspberry Pi. Cable resistance plus connector resistance can quickly reduce operating voltages below the proper range(5.25V to 4.75V).

Warning:

but also by back-powering it, you are actually bypassing the PI's input polyfuse protection device! This can have extreme consequences if ever you manage to put more than 6V on the PI, even for a very short period. As this causes the overvoltage device D17 on the the PI to trigger and short the 5V supply! Without the polyfuse limiting the current through D17, it will burn out, probably melting the PI's enclosure with it, (if you have any) and possibly causing a fire-hazard. It will probably also create a permanent short of the 5V supply! So be warned, and if you use back power make sure your hub or its PSU has a fuse to prevent this from happening. If not, add your own fuse.

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    The input poly fuse is rated max 750 mA, See the T075 on this datasheet and here. Much much better than tinkering with fuses in USB cables would be a hub with that fuse already built in when supplying back powering.
    – RolfBly
    Commented May 26, 2015 at 19:42
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Things have moved on a bit, the situation now depends on which model of Pi you have.

  • On early raspberry pi model B boards the polyfuses on the USB ports will initially allow backpowering but are likely to trip out due to overcurrent before the Pi successfully boots.
  • On later raspberry pi model B boards (rev 1 "eco1" with links instead of polyfuses and rev2), raspberry pi model A and A+ boards and raspberry pi zero boards you can backpower from the USB ports.
  • On raspberry pi model B+ and raspberry pi 2 model B boards there is a power control chip on the board. This will prevent the board from starting up under backpower from the USB ports but interestingly it will allow backpowering after the board has started.
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