Ask HN: what kind of projects could someone build in advertising/SEO space?

- I was reading the thread : Ask HN: How many of you built a profitable startup while having a day job?(http://news.ycombinator.com/item?id=3303776) and thought to work on some project that can make me learn and earn(possibly) over some time. - I am not looking for exact projects but the ideas from community as to what kind of projects one can build in areas of advertising, SEO that can also help reaping monetary benefits if project turns out to be good. - Any reference/books/blogs are very much appreciated

P.S - I am very new to the area of SEO/advertising