I have a Windows IIS web farm on EC2 that I'm looking at my load balancing options for? Any suggestions? Right now I'm using a Linux instance running HAproxy.
You might want to have a look at Apache Synapse. It is aimed more at web services rather than pure http proxying, but does have some nice features allowing not only load balancing, but the ability to spin up additional servers on EC2 in response to application load.
Check out WeoCEO - it's a load balancing appliance that spins up as an EC2 instance. It works roughly the same as conventional hardware load balancing solutions like F5's.
We've been using pound. We are not completely happy with it however. The main concern is lack of configurability for special cases and not many others seem to use it. We don't actually use it for load balancing so much as service redirection so it's overkill in our case right now.
It is packaged for Ubuntu though, which makes installation and maintenance a breeze.