Yes, I would assume that too, but I would not assume that these are applications in this case.
What I do when things look full is twofold.
From th command line (I hope you are at least vaguely comfortable with the command line), as root try
You should get something like
]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 29G 5.6G 22G 21% /
/dev/sda1 99M 24M 71M 25% /boot
tmpfs 753M 0 753M 0% /dev/shm
/dev/sda3 263G 93G 157G 38% /home
/dev/sdb1 276G 189G 73G 73% /storage
I'd then cd into /home and start digging around with du to work out where I should start. Try (again, as root)
du -h --max-depth=1
and see how that usage is distributed. Then we can give you some more ideas.