Ever wonder what the world would be like without inventors who created products for our every day problems? For example, take the lids on disposable soft drink cups. I remember the days when I ordered a soft drink from a fast food restaurant, they would mark the lids of the cups with either a "D" or "R" for "Diet" and "Root Beer" respectively. Now they just push down on the little plastic bubble on the lid to indicate the kind of soft drink inside.
How about the bendable straws? Before this invention, patients in hospitals would frequently spill their drinks while drinking in bed. Now with the bendable straw this is no longer a problem.
These are all simple solutions to problems. I believe the best solutions are the ones that are simple, and the best candidates for innovative solutions are those everyday problems that people constantly take for granted.
So, if you're a closet inventor, pay attention to those every day things you take for granted. Some of them may turn into great inventions.