find command

To list files that were changed in the last day, sorted by size, using Apple’s Terminal, or any Unix / Linux bash shell:

> sudo find / -type f -mtime -1 -print0 k
 | xargs -0 du -sk | sort -nr

(thanks mynamewasgone!)

Command breakdown

run in superuser mode - allows you to reach hidden system folders (if that's what you need). You'll be asked for your password
find /
use the powerful find command, starting from the root of the computer - in other words, search everywhere (which may not be a good idea if you are connected to a network or have a massive hard disk connected to your machine)
-type f
only look for files...
-mtime -1
...modified less than a day ago
when files are found, spit them out in a list with a NULL at the end instead of a new line - this helps with the next step
pass the list generated by find to the next command...
xargs -0
...which is xargs, used to take a list of results and pass them on. The -0 is telling xargs to use NULL as the separator
du -sk
use du to show how much space the files take, in kilobytes
pass the list generated by find to the next command...
sort -nr
...which sorts the list in reverse numerical order using sort

Find -exec is slow

Originally I did everything within find, using the -exec flag.

$ sudo find / -type f -mtime -1 -exec du -sk {} ; | sort -nr

But as mynamewasgone pointed out, find -exec is slow