There are several choices.
For deployments, you could use either chef or puppet. Neither one is clearly better than the other. I have found that chef-solo serves my needs
For network health, amazon offers cloudwatch (expensive and not that powerful and not open source, imho). You could set up a zenoss box and use the ec2 "egg" to automatically monitor you servers over snmp, but its a pain to configure and is another server you need to maintain,
My favorite offering dejour is scoutapp. It is not open source and it will cost money, but it lets you monitor all of your servers, will page you if things go down and will allow you to post arbitrary key/value pairs to track anything in your system (including business metrics).