Disclaimer: I work at Cloudkick.

We can help you all with these problems.

Here's how fast/easy it is:

1. Create an account (~30 sec)

2. Add your cloud credentials (~45 sec)

3. Install the monitoring agent (~90 sec/node)

4. Create a CPU/Memory/Disk monitor, query-targeted all your servers (~60 sec) (example: "provider:EC2")

5. You get an email whenever the monitors you created reach the thresholds you set

There are a lot of other cool features - check 'em out on the site: www.cloudkick.com

All our plans are free for 30 days.