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That depends on a number of things. Is this your only partition or do you have /home mounted on a separate partition? What distribution are you using? Is /var a separate partition? Could you give us the complete output of df ?

it looks like you have everything (except for /usr) on that partition.
df -h makes it a lot easier to read things.
most likely you have a lot of stuff under /home and/or /var
for example you could use du -sh /home/* to check for disk usage under /home for each directory.
you can try cleaning the log files (/var/log), check for stuff under /tmp and /var/tmp check for databases/log (mysql stores them under /var/lib/mysql but DON'T delete anything from it unless you know exactly what you're doing)
you could also try running eg.
find /home -type f -size +100M
it display any file bigger than 100MB under /home and it's a good way to find stuff that you forgot to delete (archives) eating up your disk space