One of the interesting things I have learnt is that internet is old enough that anything interesting or valuable you want to do on the web has a lot of stiff competition.
There is a lot of competition if you don't want to look further than what is currently on the web.
The web started with static content sites. The web is now full of content sites and it is difficult to compete with a new static content site.
Then came the sites to find those static content sites. Search engines and directories. That path is also beaten to death now. It is very difficult to compete with a new directory or search engine nowadays.
Then came the sites to link people. Dating sites, all kind of social networking sites. The area has been filled and is difficult to compete in with a new site.
So what's next? Think, think, think and look at yourself. Don't look at others, but look at yourself. What are you using a computer for locally and why shouldn't that be interesting for others? 20 years ago I made a small computer program to assist my mom with something. The program source was just somewhere in a corner of my hard disk until I stumbled upon it a few months ago. I then thought, "Wouldn't this program be nice for other people in the world?". The conversion to a web based application took a few weeks and it is now already taking off with almost no competition in that area.
The near future is not content, search/link or social. The near future is on-line services where people can do what they used to do locally, but now with their smartphones, netbooks and other small computer devices where they don't want or can install software locally anymore. Open your mind, look at yourself and jump into services. Monetizing will come.