I'm looking for any available free Excel "helper" classes that are written for .net (doesn't have to be C#). I'd like to evaluate what others consider to be useful and generic static (and non static) helper methods. Can be targeted at VSTO or regular Office automation, although that probably doesn't matter.
I guess I should also point out that this question is NOT asking for "what are good alternatives (or free alternatives) to using Excel object model automation. I don't really want links to SS gear, etc, although they are all great products that's not the purpose of the question.
In case I wasn't clear enough in the previous paragraph: I don't want answers that state - use this free (or not free) 3rd party component, instead of Excel object model code.
So basically what i was asking for was user developed C# code libraries that contain VSTO, Office or Excel helper functions such as static methods for working with menus, ribbons, ranges, workbooks, documents, xml (such as the ones otaku mentioned)...