I want to agree with the previous post (Uncle_Theodore), but it occurs to me that you may need a bit more explanation and some more detail.
One of the big advantages of the unix-style system for naming partitions, as opposed to partition letters, is that you can 'hang' new partitions/disks almost anywhere in the tree of names.
To take a simple example, if you only had a single user workstation you might find a few gig appropriate for /home, and you might not have /home as a separate partitions. If, then, you wanted to use that box to host ~6 user accounts you might find it appropriate to have a separate partition (either from spare space on the existing disk, or from a completely separate disk) for /home. Or, probably with a larger number of accounts still, you may even want to keep some user accounts on one disk and some on another, for performance reasons. You can see how this makes expansion easier.
And its as simple as making sure that the partitions has an appropriate format and /etc/fstab is correct for the mount point (your distro may have a tool for setting up the partition and the mount point, depending on distro).
You have already used quite a bit of space for /home, so exactly that may yet happen to you, but exactly the same principle applies to /opt.
Note also that you do not need to adopt the same 'formats' (filesystem types) for the different physical partitions, and if this a seriously used box you may want to think about that: You won't get a single-valued answer to which type is best, but I tend to use ext2 for /boot and reiser for pretty much everything else, with 'atime' turned off. You will certainly hear arguments that ext3 is a better choice than reiser (and there is xfs and jfs and (somewhat experimentally) reiser4 and ext4, depending on distribution and the degree of confusion that you are prepared to contemplate), but I would advise the selection of a journalling filesystem, usually ext3 or reiser, for at least the user data (maybe others as well if you have other frequently changing data and an infrequentunreliable backup system).
I'd try to keep to two or three different filesystems, max, for the box as each filesystem brings in the requirement for a new driver.
So, for example, there may be a performance boost by turning journalling off ('nojou' on reiser) for /tmp, if that is a separate partition (but you might not like the occasional boot delay for an fsck if you use a non-journalled system). Obviously (??) if /tmp is just a part of / and not on a separate partition, you can't 'tune' these parameters for the individual partitions, because they aren't individual partitions.
In truth, the performance of the different systems probably depends as much on setup (file system tuning) and load profile as on the fundamentals of the file system itself, which is what makes '...and the best file system is...' so difficult.