Use the find command to find all files above a certain size:
find <directory> -maxdepth 1 -size +100M
The -maxdepth 1 option will prevent recursively transversing subdirectories. I don't know if you want to do that, but if there is a subdirectory with a large number of files and subdirectories, this can save considerable time if they aren't of interest.
Also read the "man file" manpage. The "info file" manual has a number of examples for more esoteric uses such as finding suid files or formating the output.