Similar to BradB's triage system I'd use the categories Act, Read, File and Bin.
Act means this is something you have been asked to do and it's your responsibility to do it. Do this stuff first after categorising.
Read means it may contain useful information, but you don't know yet. This also takes those magazines and CPD activities. Pick up this stuff when you hit a mental block on the work you are "Acting" on or in the time you put aside for CPD.
File means it contains relevant information about a decision or work done that needs to be stored for future reference.
Bin is just as it says.
Start by moving all items in your inbox to one of these categories, as you act upon or read stuff move it to file or bin as necessary. Clear out the File stuff at the end of the day, and only check your inbox when your programming work hits a natural break and you are not "in the zone".
It doesn't address how to file stuff, but that is an individual thing anyway.