Well, I know this may not help you the greatest, as I'm not a huge succesful webmaster or anything (yet,

), but these are my opinions.
First of all, I feel that the best places to get website ideas from is the Internet itself. Explore, and learn what is popular, what isnt, what's succesful, what isn't. Look at succesful, popular websites, and try to figure out what they are doing right, and do the same for less-succesful/popular websites, but figure out what they are doing wrong.
After taking what you have learned, you may or may not be able to apply your findings to pre-exising ideas and make them work, or possibly come up with brand new ideas.
Also, one thing to remember. Look at some of the worlds (and the nets) leading companies. In the beginning for a large majority of them, people may have thought nothing of them, not expecting them to amount to anything, but a LARGE part of business is taking a chance, and IMHO, this is a large part of the internet. Of course, you don't have unlimited resources and time, so you need to find a good area, where you arent giving everything away.
Now, people may largely disagree with me on everything I've said, and thats fine, I'm just expressing my opinions. Not everyone agreed with Karl Marx, right?
Good Luck!