Woah...remind me not to visit your house.
Here's some things I found about snakes.
Keeping Snakes In Their Place
WikiAnswers - How do you keep snakes out of your yard
As for killing weeds. Do you have grass in your yard? If so, just let it grow long and thick and make sure to overseed every year. That should choke out most weeds. The only other thing you can do is fertilize it with some kinds of natural fertilizer. That's all I got.