I want to give /dev/hda1 (for /tmp, /var etc) more space from /dev/hda8 (/home). I'm using Slackware, what's the easiest/safest way to do this?

Errr, isn't there quite a few partitions in between these two?

I have hda1, hda6, hda7, and hda8. I want to move space from hda8 to hda1 because hda8 has the most amount of free space and hda1 is in need of more.

Well if there is enough free space for your /home on hda1 then backup both hda1 and hda8 format both partitions restore what was on hda1 to hda8 then hda8 to hda1 change your /etc/fstab & menu.lst/lilo.conf if using it to reflect the new order of things and use your machine that way probably best done using a live CD so nothing is running on your system at the time. Another alternative method of doing the same thing would be if there is enough extra free space on the hda8 to hold your entire hda1 the you could copy it there instead of backup format/delete the files from hda1 move the original /home files and you achieve the same results without having to do a backup first.

if they are ext2 or fat then boot off of a live CD that has GParted, have some blank space(Unformated section), and then try moving the partitions