I don't know much about VSTO or VSTA, but I think you need the full version of Visual Studio to use either one. I can't convince my boss to buy us this, but I would like to develop Excel addins in IronPython. I've looked at several tutorials that show you how interact with Excel using IronPython, but I can't find much about developing addins. Can you recommend any resources?
Is my only option making a COM addin? If so, does anybody know of any example of this using IronPython?
I'm sorry to say I can't go with any options that include spending money. I've got the free Visual Studio Shell and IronPython tools for visual studio setup for free right now.
First, you are right, unfortunately VSTO is not supported in Visual Studio Express, the free version of VS.
Then, you may want to look into ExcelDNA. I haven't tried it specifically with IronPython, but it should work. ExcelDNA is a free library which allows you to build xll Excel add-ins and use .NET, up to version 4.