IF you have multiple devices that take 5V then, in theory, one supply with a higher current rating would let you charge multiple devices in parallel.
Many mobile phones, for instance, now use a standard mini (or micro) USB connection. They look for a charger with the D+ and D- pins shorted, or with a maximum of 200 ohms across them. Apple, being different, looks for specific voltages on these pins. Look up Adafruit for more details on this.
If you need other, or multiple, voltages - things get tricky. "Dangerous Prototypes" have articles on converting an old PC power supply into a voltage source. If you need 12V this may be the way to go.
Finally, a switch-mode supply is better than a transformer. Never mind the efficiency - if you want this for travel you could end up in a foreign country, with different mains voltages, frequency... and power point. With an SMPS you just need a powerpoint adaptor.
EDIT- For follow up questions - transformers have losses related to frquency of operation. The lower the frequency, the biiger the transformer needs to be. Their output is also proportional to their input, divided by the ratio of turns on primary & secondary. So, a tranformer rated for 240V 50Hz ac, giving 5V out, would be ok running on 115V 60Hz - but it would give less than 2.5V out. A 60Hz core running on 50Hz mains would have larger eddy currents in the core, and risks overheating.
Simplifying GREATLY - a SMPS takes your input volts, and converts straight to DC. It then "chops" that at a very high rate, and shoves the result into a much smaller transformer. The output is monitored, and the pulse width of the "chop up" section is adjusted to get your desired voltage. Different voltage, from foreign country? Meh - the circuit just changes pulse width to compensate.
YES you can have multiple output voltages. However, feedback is typically only on one of them. Computer suppplies [see above] typically have +12V and +5V. Some have -12V, some even have +3.3V but that's not so common in PC supplies [yet].
Details of the ATX breakout board are at: http://dangerousprototypes.com/category/atx-bb/
Here's the problem - excessive inrush current is when the transformer is activated close to the AC cycle passing thru zero. Consider the steady-state case: -
Current lags at about 90 degrees and if you applied the supply voltage close to when the voltage peaks, current will naturally not have the problematic inrush state: -
When powering the transformer with a supply voltage passing thru zero a much larger flux density occurs and this saturates the core causing (sometimes) a massive over-current.
If you can find a motor protection device that explicitly states it performs the above function then it should be OK.
Best Answer
To clarify what Brian Drummond is talking about with "C" or "D" type circuit breakers - "C" type is for general purpose loads. "D" type is for loads with a high inrush current.
Using a "D" type breaker might allow the circuit breaker to restrain from tripping on inrush curent.
Excerpt from the Clipsal 4-series miniature circuit breaker catalogue:
With regards to soft starters;
It depends on the type of soft starter.
Some use an inductor or resistor or auto-transformer in series with the load, to reduce the starting voltage and hence the starting current. The inductor/resistor/auto-transformer is bypassed after a few seconds. This type would likely work well for you.
Electronic soft starters use some kind of semiconductor device (usually thyristors) to do pulse-width modulation of the voltage. This is a bit harsh and your machine may not like it.