Induction requires devices to support it, though you can retrofit various devices (either yourself if there are some AA type replacements around or with third party) it is not that viable in a lot of cases and doubly so with portable devices.
Step one would be to look at all of them as see what connectors, voltage ratings and current requirements each of them has. Depending upon your setup you may have to calculate for a worst case scenario (every device you can connect all connected at once, it might be more aggro than it is worth to do this so you might knock it back a bit and have 1 3ds socket and so forth).
Rather nicely most devices these days will charge off 5V and some form of USB (or have very cheap USB charging adapters). Those that are not USB tend to be 12V or 3.3v (though 3.3V can be made from USB voltages easily enough). 12V is what comes out of car lighter sockets so if you have a GPS or something... For the record USB delivers 5V and can deliver up to 500mA or 0.5A, not all devices with a USB adapter will need all that current and though they will tend to have limited current options so you can use USB there are many devices that will take more current if it is offered (Apple, kindle and such like "fast" chargers being a good example of this, most of the time this involves sticking a known resistance across the signal wires (USB is four wires -- positive, negative and two signal wires)), if it bothers you just remember basic USB will still get it charged.
The ugg ugg grunt approach (one I must confess that I favour in most cases) is to get a whacking great transformer/PSU with 5v +12V + whatever else taps/rails that is rated to deliver the worst case scenario current and stick a bunch of adapters and a couple of USB sockets for good measure in parallel before wiring it all up. If you have to ask and
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM is troubling then buy one in. If said link makes sense then you have a project for the weekend.
For the most part this is all old school analogue electronics so if you know how to add up current for a rail, know the difference between series and parallel and "check the polarity" is a phrase that makes sense to you then you are good.
The slightly more civilised approach (which may or may be £20 cheaper) involves considering electronics, adding in current dropout negation, full on regulation, maybe considering noise and such like. Most good transformers will handle this happily and the only reason I would consider it is was if I was making a paid "charge bar" for someone.
For giggles I would also add a cheap 5 way "universal" power supply end for those times you dig something out of the cupboard or have visiting relatives though you might want to add some more current supply capability if your worse case scenario is what you got a power supply rated to handle.
I would ignore old mobile phones unless you have to support them, I would ignore laptops for the time being unless you want a headache.
If you want to get really creative you can add a continental/US power adapter on it, frankly I would not bother.
In short your shopping list is
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM (old knackered PC and a trip to maplins should be able to handle this).
A 3ds USB cable.
http://www.amazon.co.uk/Nintendo-Charger-Cable-Digital-Accessories/dp/B005HNY1VE/
An apple charge cable. Poundland will have some. Do note they did change up the cable style a while back so you might have to get two. You might instead prefer to get a dock of some form and cannibalise it.
Some USB sockets. I tend to pull them off dead devices and maplins do not always have them but you can do what you like.
I suggest a USB cable, a microUSB cable and a miniUSB cable to add to this.
A car lighter/power socket. I go in car parts places often enough and they have them there. Usually only a couple of quid anyway unless you want to go for a multi socket thing (though there are cheap ones even then
http://www.amazon.co.uk/TRIXES-Socket-Cigarette-Lighter-Adaptor/dp/B0053X5TG4/ ).
A throwaway "universal" adapter. Cheap shops like QD will do this.
The rest is basic screwdrivers, project boxes, hot glue and a bit of solder. I suggest you attach the cables somehow to avoid a case of wandering cable, an unpleasant affliction that usually troubles those with a larger family.
If we are going crazy and throwing an ipod dock and speakers into all this then urgh but it can be done.
The only problem with all this is people like to watch TV with things charging, be in bed and doing as they charge and generally have them with them. Such things are kind of difficult if they are in the kitchen/on a shelf somewhere, of course if your are not cannibalising your existing gear then you have the all purpose get out of the debate phrase "shouldn't have lost/broken your charge cable now should you".
