Number of files with specific file size ranges
suffixes = ['B', 'KB', 'MB', 'GB', 'TB', 'PB'] you never change the value of suffixes, so it should be a constant, the standard naming of constant in Python is  ALL_UPPERCASE, rename it to SUFFIXES
You should name variables with snake_case.
You wrote for r in files: the details count: the standard one-letter identifier for file is f, use that.
Look at f = ('%.2f' % nbytes).rstrip('0').rstrip('.'), f is a meaningless one-letter name. You should use a longer and more meaningful name
You are checking and i &lt; len(suffixes)-1 in the loop: it is not possible that the user has a file bigger than one Petabyte (10**15 bytes) so you can safely remove that check. and it is very good that you that, code that crashes when you find an unexpected condition should be avoided with error checking like this one. (Thanks to @Veedrac for correcting me)




f = ('%.2f' % nbytes).rstrip('0').rstrip('.')
return '%s %s' % (f, suffixes[i])


You are a C programmer, aren't you? :) Using "%s" string formatting in Python is considered obsolete and should be avoided, instead use string.format()



print "Number of files greater than %s less than %s:" %(human_Readable(start), human_Readable(end)),  counter


You are printing from inside a function this is not nice, you should return values, not print them.



It is common to take the parametres from the command line so:

route = raw_input('Enter a location')


should become:

import sys
route = sys.argv[1]


this also makes the code compatible with Python 3 if you add brackets around the print 



You are repeating yourself so much:

file_Dist(route, 0, 1024)
file_Dist(route,1024,4095)
file_Dist(route, 4096, 16383)
file_Dist(route, 16384, 65535)
file_Dist(route, 65536, 262143)
file_Dist(route, 262144, 1048576)
file_Dist(route, 1048577, 4194304)
file_Dist(route, 4194305, 16777216)


It would be better to use a loop:

for start in [1024,4096,16384,262144,1048577,4194305]:
    end = start * 4
    file_Dist(route,start,end)




You may want to import this script, using if __name__ will allow you to run the tests only if this script is the main file

def test():
    for start in [1024,4096,16384,262144,1048577,4194305]:
        end = start * 4
        file_Dist(route,start,end)

if __name__ == "__main__":
    test()