ほど indicates degree or extent, and is usually used with a negative verb. It follows the pattern:
A wa B hodo [adjective]-nai.
Ex. Kumiko-san wa Mai-san hodo sei ga takakunai.
Kumiko is not as tall as Mai.
Ex. Kumiko-san wa Mai-san hodo Eigo ga heta ja nai.
Kumiko is not as bad in English as Mai is.
This is the most common usage of ほど. It can also mean "to the level of", as in the following:
Kono manga wa akiru hodo yonda.
I read this manga until I got tired of it.
More interesting, though, are some expressions which utilize hodo.
This means "the more...., the more...."
Kare no koto wo shireba shiru hodo wakaranai.
The more I get to know him, the more I don't understand.
(Lit. If I get to know him, I will not understand to the point that I know.)
As you can see, it's better just to understand this phrase as a whole. :)
Anohito no kotowo suki ni nareba suki ni naru hodo kokoro ga itai.
The more I get to like him, the more my heart hurts.
"There's a limit to...."
Gaman suru nimo hodo ga aru.
There's a limit to my patience.
(Lit. There's a limit to how much I can bear.)
Joudan ni mo hodo ga aru.
This is no longer a joke!
Lit. There's a limit to jokes.
3. これ、それ、あれ + ほど
Means "of this/that extent"
Korehodo muzukashii to omowanakatta.
I didn't think it would be this difficult.
Sorehodo okane ni komatte itara doushite hitokoto, soudan shite kurenakatta no?
If you were that desperate for money, why didn't you tell me?
(Lit. komatte -> komaru -> be in trouble)