Kreyola did an awesome post on oils and locks. Here is a snippet:

Now there are many carrier oils and essential oils out there, but I'm going to list the common ones for hair and hair related issues.

Essential Oil
Benefits
Tree Tea Oil
Control Dandruff & Dry Scalp
Rosemary Oil
Hair Growth - Reduce Hair Thinning & Hair Loss
Sage Oil
Prevent Dandruff - Strengthens the Hair Follicles
Peppermint Oil
Cooling effect to the head - Removes dandruff & Lice.
Cinnamon Oil
Thicken the Hair - Scalp Circulation

Carrier Base Oil
Benefits
Jojoba Oil
Light Moisturizer - Fungicide - Mildew Controler
Avocado Oil
Heal Scalp - Hair Nourishment - Hair Growth
Olive Oil
Control Dandruff & Dry Scalp
Coconut Oil
Softens Hair - Conditions Scalp
Castor Oil
Hair Growth - Reduce Hair Thinning

Please visit: http://kreyolalocks.blogspot.com/2010/11/essential-oils-vs-carrier-base-oils-on.html for the entire post.