Stop server crash

Stop server crash

I run my python scripts and Scrapy framework for web scraping project on
my Ubuntu 12.04 precise server. These scripts run whole day.
This project is under developing/testing stage. So i dont know what will
be the system requirement of this project.
I started it with 512MB RAM and 30GB Hard Disk. The system crashed because
of less hard disk space. so once again i have to setup the server and
restarted my project with 512MB RAM and 100GB Hard Disk.
Again the system crashed because of less RAM/SWAP size.
Is there a way to apply checks on RAM, Hard Disk ? So that beforeserver
crash it will kill all the programs and send me mail that all programs are
killed because of less space increase your RAM/HARD DISK size.