My interests and areas of (amateur) expertise are history, current affairs, neo-darwinism and linguistics. I also have some professional expertise in other (completely unrelated) areas but that's work. Of my amateur interests history (particular military history) and current affairs would be the two that I would feel competent to edit in Wikipedia. This is not a testament to my brilliance in those areas but rather reflects the low standard in those areas of discussion (as compared to say the sciences). The low standard I refer to is not a criticism of wikipedia specifically it is more general. Much of the generally accepted history of the last century is rubbish and almost all the current affairs commentary is utter rubbish (hence the disaster in Iraq).
So on wikipedia I am doing my little bit aginst the tide of junk.