screen broken
My screen is broken and homekey is disfunctional
iPhone 4
This is suprisingly easier to fix than you think.
For the Homebutton you can use something called assitant touch which will peform the actions by pressing a button on the screen. http://snapguide.com/guides/activate-assistive-touch-on-your-iphone/
To fix the screen you can dismantle your Iphone and melt the glue holding the screen and mid frame and replace it for around $30 (AUD) tops. If you don't feel safe doing this you can take your phone to a professional or a store in your mall or marketplace and they'll do it from $40-60. There are lots of good tutorials on youtube.
If you really want to fix your home button you can take your phone apart and replace the flex cable. This is difficult and slightly dangerous becasue you take out the motherboard. That will fix all buttons. I'm planning to do that on my iPhone 3Gs.
Hope that helped!