Is there any software out there that can simulate complex control circuits so the the logic can be tested before construction?

If it's complex enough to use a programmable relay, you can test with the programming software.

I was wondering about PLC software. I'm not using PLC's for various reasons. Would I be able to purchase and use the software as a simulator without a PLC? Any suggestion on user friendly software?

Here is a link to zelio:
http://zelio-soft-2.software.informer.com/
I'm on the wrong machine so I'm not 100% certain of the link. The software is free and the smallest relay is about the cost of a couple TDR's, so it's reasonable.

I have used another make, but they charge for the software.

Thanx!

You can also try Automation Direct, free software (Click), a Click PLC is about $70, you might need a small power supply if you don't have one. The programming is about as easy as it gets, I use it to teach ladder logic & PLC programming.