/boot = 50mb
/ = well.. whatever really, if that's going to include /usr then maybe up to 8gb.
if you're after moving the data from your existing /home directory to it's own partition you'd need to do something like this:
mke2fs -j /dev/hda5
mount /dev/hda5 /mnt/home
find -xdev /home | cpio -pvd /mnt
that will clone the existing home onto the new partition exactly (hopefully)
the -j option in mke2fs creates a journal, which means it is actually ext3 not ext2. also fdisk doesn't do any formating at all. it's a partitioning tool only.