You can do that with LILO or GRUB. I prefer GRUB though, it's a little easier. All you have to do is tell it where the kernel and root directory is for your other distro. Just edit /boot/grub/menu.lst (it seems this file can be in multiple places under multiple names, like /etc/grub.conf, or /boot/grub/grub.conf). Add a new entry to the menu like:
kernel (hd0,0)<path to your kernel> root=/dev/hda1
kernel (hd0,1)<path to your SUSE kernel> root=/dev/hda2
Replace the (hd0,0) thingies with whatever partition the distro is on. For reference, I believe it goes something like:
hda1 = hd0,0
hda2 = hd0,1 ... etc
hdb1 = hd1,0
hdb2 = hd1,1 ... etc
In other words, a distro with its root directory on hdb1 would go something like this:
kernel (hd1,0)/boot/kernel-2.6.1 root=/dev/hdb1
You should get the picture. Make sure the "root=/dev/<hdxy>" points to the distro's root partition as well.
I hope my advice doesn't screw up your computer, good luck!