yes Feeb, I've heard sitting wrong way round (or right way round heh heh) on the toilet can work well, esp with a pillow on the cistern to make it more comfy ... and maybe someone aiming the shower head at your lower back!

Sitting & rocking on the birth ball can be nice too. You can circle your hips too, especially in a clockwise direction which can help a baby move more anterior. The only thing is, don't stay like that too long without a break, get up, move around to encourage blood flow and oxygen to all areas.

The birth pool is my best bet for excellent perineum support and least chance of tearing.
At the NCT class in England, our instructor suggested I sit in a bucket in the birth pool.

Huh?

Yes I know it sounds strange, she said. Then she produced a bucket and asked me to sit in it. Not on it. In it. I saw what she meant. It was the perfect height off the floor for a supported squat, and the rim of the bucket was just nice for support for my seat. Then she added a folded towel for more padding. It was ridiculous how comfortable it was.

During labour, I had a bucket in the birth pool with a brick in it to stop it from floating off. I sat in it on a (wet, obviously) folded towel to rest in bt contractions, and could stand up and lean over the edge of the pool during contractions.

I alternated the pool with upright standing/swaying moves. Pushed on all fours because I had pretty tender haemorrhoids (sorry! TMI alert - but I know I have one 'sister in suffering' on that count - ) and standing squat was too intense on that region. No tearing but my babe was only 7 pounds so I guess I was lucky! Still, my friend's first (also a homebirth) was 9 pounds and likewise no tears. I think having the freedom to move instinctively as you wish and do what YOU feel you need to do to birth your baby helps a lot.

Nuther tip for birth pools - floating bubblewrap on the top keeps it nice and warm while you're not in it.