Is software development tax deductible if you don't pay yourself a salary?

New businesses don't become profitable over night. There is a period of time where you're making money, but you don't have enough money to quit your day job and start paying yourself a salary. In this case, what exactly can be written off at tax time?

Off the top of my head, I'm thinking development involved in creating new features and/or products is tax deductible. Also, the software product itself must hold some kind of value.