Simple fc2 default install has my disk as follows: /dev/hda1 98meg /boot 85.4 meg free /dev/hda2 71gig / 62 gig free.
Lots of free space then. You could boot from the rescue CD, not mount your filesystems, then use resize2fs to shrink the size of your root filesystem (/dev/hda2) to say 20G, then use fdisk to reduce the size of that partition to whatever size you actually wanted (> 20G) and then finally use resize2fs to grow the root filesystem back to the size of the partition (this convoluted scheme makes sure that your filesystem never exceeds the partition size at any time). This would leave you with whatever space you had reduced the partition by to use for new partitions, which you can add using fdisk.
I would like to have a /usr/data structure (or /data) where I store data from ALL apps.
That should be fine.
Also, a /usr/myPrograms structure, for programs that I 'manually' (not from the distro) install.
These are usually put in /usr/local so you might have a separate partition for that.
Paul.