These have all been tested. Anyone have any four potion recipes?

Paralyze+damage health+lingering damage health

Imp Stool + Human Flesh + Slaughterfish eggs/scales.
If you cannot find human flesh you can substitute Canis root. You can also substitute mora tapinella for the slaughterfish ingredients.

Weakness to poison+damage health+ravage health

Deathbell + Skeever tail + Giant lichen

Damage health+damage stamina

bonemeal + jarrin root + ectoplasm
bonemeal + void salts + jarrin root
bonemeal + skeever tail + nirnroot
bonemeal + cyrodilic spadetail + silverside perch
blisterwort + red mountain flower + nirnroot

Paralyze+poison

impstool + human flash or canis root + slaughterfish eggs or scales

Damage magicka+poison

red mountain flower + deathbell + lavender (a huge amount of deathbell, as well as swamp fungal pod, can he found in the swamps around Morthal)

Paralyze

skeever tail + void salts
swamp fungal pod + canis root
swamp fungal pod + briar heart
canis root + imp stool
canis root + human flesh

Slow

large antlers + salt pile
river betty + salt pile
river betty + namira's rot

Two good alchemy recipe websites

http://skyrim.melian.cc/?cmd=cmdSkyrimAlchemyWizard
http://potionapp.com

Good list - thanks. Bear in mind that not all damage health poisons are equal - mix a poison with a crimson nirnroot and notice how powerful it is in comparison with say imp stool and nightshade. I tend to go with a simple damage health poison a lot of the time - few effects mean a cheaper potion so it is easier to reverse-pickpocket.

I use Imp Stool, Canis Root, and a River Betty for a good paralyze & damage health poison. I don't worry much about the lingering effect since I tend to kill them while they're paralyzed anyway