How to find all files with size greater than...?
In the shell tools we have
find
:find / -size +1M
For files over 1 megabyte.
And in the GUI's we have the Disk Usage Analitizer (baobab):
sudo apt-get install baobab baobad
There is a bunch more on this question of SuperUser, but for all ends and propose baobad is enough.
When I need make more free space on servers I use this command. It find all files bigger then 50 MB and "du -h" make berret list of files and "sort -n" after pipe make list numericcaly sorted by file size.
find / -type f -size +50M -exec du -h {} \; | sort -n
gnome-search-tool
is what I use. Very simple. It has the "Size is at least" filter where you can specify minimum file size. See screen print for searching my ISOs folder with a minimum size of 10,000,000 KB in size.