What kind of major issues are you having distributing things across AZs?
The first step is identifying what's not scaling. Is it your process or your application?
Personally one of our favorite pieces of software is Zookeeper -- it makes everything stupid easy to keep some shared metadata and do service autodiscovery / autoconfig.
Another good tool we use is Storm for writing real-time systems, it becomes a simple matter to deploy a large real-time system on top of any number of EC2 instances.
Michael Rose
FullContact