Hi Jon,
It may be worth checking out Google Trends as well.
It is still in Beta so the stats may not be great but along with Google's suggestion tools, it may give you an idea of what people are looking for.
General advice would be that look around you to find a niche. You should look at niches for products you can mass market
Example - we do
prepaid cards .
Credit crunch means less credit, more prepaid. However, that is not the end of it. We have a product on our site called BabeeCard.
BabeeCard is for young and expecting mothers for all their purchases.
However, new scenario - credit crunch, mothers going back to work, mothers need nannys, so is the BabeeCard now also a nanny card? See where I
am going with this.
Choose a product/service you know loads about and then learn about it and develop a niche as you go along.
Thats my two bits anyway.
All the best
Ash