I'm looking at a product that was coded in a mix of .NET and ASP Classic. I'm wondering if it's possible to get this running in Linux? I've heard of Mono (which can supposedly run .NET on Linux) and Sun Java Web Server (which can supposedly run ASP Classic on Linux). Are there any other technologies that you would recommend?
Also, are there any major pitfalls that I should be aware of?
Mono works great for ASP.NET. They have an entire site dedicated to ASP.NET on Mono.
Probably the best resource for things to watch for is the Guide to Portion ASP.NET to Mono page. It walks through the changes required (if any) to get an ASP.NET project to run on Mono.
Mono does not, however, support ASP Classic. The best option I've heard for that is Apache::ASP, although it does have limitations, such as not handling VBScript or JScript without 3rd party, commercial tools.
Getting it running on Windows is going to be tough enough, when you consider that the version of Windows / IIS it was developed on are probably no longer supported.
Does your application have extensive auto tests? I'd hazard a guess at probably not.
The best bet for getting it working is to (If your ops team will permit it) buy licences for the ancient version of windows it was built for, and run that on VMs on whatever OS you want to use on your hardware.
The old version of Windows your app was written for (e.g. Windows 2000 server) probably won't work on modern hardware, or at best will be unsupported by your hardware vendor. Therefore you have no option but to either run the app on a newer Windows (Bad; this will introduce subtle bugs that you cannot test) or run it on a legacy Windows in a VM.
If the application is to be exposed to the internet, running an old version of Windows (even fully patched) is not really a good idea.
Rather than trying to put a round peg into a square hole, try to work out the minimum-risk way of continuing to run the legacy app while your development team fix it, develop auto-tests etc.