Hey does anyone know how to make potions & poisons without having alchemy as a major skill? and how to know which plants to use to make for example, "potion of healing" ? thanx

Not having Alchemy as a major skill is no problem; lots of people prefer *not* to have it as a major skill because it tends to level up very quickly. As a minor skill, you can use it as much as you want without leveling up your character in the process, and it'll help you gain Intelligence.

There's a full ingredient/effect list at the Wiki. Link is http://www.uesp.net/wiki/Oblivion:Ingredients

In all my play throughs I have never used alchemy as a major skill (it levels too quickly) but always made poisons and potions use the link that UnclePain has provided.

http://oblivion.melian.cc/

Darliandor's Alchemy Lab has links to everything you could wish to know about alchemy as well.

Alchemy is one of the most interesting things in Oblivion and finding out what ingredient that goes along with what is ever so much fun. So sorry, I won′t take it away from you. It′s much more rewarding to find out for yourself

In time it′s also a very powerful thing as your knowledge in Alchemy increases