I agree with Pebbles, jojoba is one of the best oils that you can use for a hot oil treatment. You can also use Olive Oil, Extra Virgin Olive oil (my preference), or castor oil. It really depends on what you prefer.
Now when you get into Essential oils, you have to remember that they are extremely concentrated so you would only want to use a little with one of the oils above.
Tea Tree is really good for the scalp. Rosemary is very stimulating and is good for growth, there are a ton of essential oils out there that are really good. Just be sure to mix essentials with some type of carrier. Also, some people have bad reactions to some of the stronger oils (rosemary tingles, but sometimes it burns depending on how sensitive your scalp is) so you should always start out with small amounts until you find just the right blend.