They don't really exist. Not unless you're coding for IE only, that is. IE5+ on the Win platform (and also IE5 mac I think) will allow you to use a height of 100% and contain the iframe in a table to control the height, but most other browsers will default to a set height, say 200px to 300px as a guess, when you do that.
I remember seeing some javascript fixes which resize the iframe height based on the browser window, but they don't really work that well.
The other problem is you'll kill accessibility by using them. To avoid that you could try using divs there, with the overflow feature specified.