The categories right now is very limited. You should add the option for people to enter a new category when they submit their app.
I guess my point is that categories are a bad idea. You put MailChimp in sales, but it should be in marketing. Then again, what is the difference between marketing and sales? Productivity is really a subcategory of all the others. You could have a productivity app that focuses entirely on client management, but then that would be called a CRM.
Don't really have a solution, just found it confusing as it currently is.