Recommended: 100mA
You should not draw more than about 100mA from the USB ports.
Source
In reality, it is more complicated than this.
I've taken two screenshots from the Device B schematic (released here):
Power in (fig A):
We can see that the 5 volt line (+5V0) is powered directly...
How can I have multiple USB peripherals connected to my Raspberry Pi at once? For example, I want to have a keyboard and a mouse plugged in at the same time.
@Alex, I think it's unlikely that anyone will assume it works differently. The question is about USB not about the Pi. Also it may confuse people looking for the related question of what powered USB hubs do/do not work with the Pi.
(not sure if that has been asked on the SE site; It has been asked on the forum.)
I think you're overestimating the knowledge/understanding of some users - I can imagine when the Raspi is used for education lots of students will google for this answer
This is completely dependant on the Class of SD card you are using.
A Class 4 card, which is the minimum recommended has an average read/write speed of 4 MB/sec.
If you spend a little extra and buy a Class 10 card, you should find that the boot time is approximately 25% of the Class 4, as it sh...