There are 2 main angles you can take:

1) Main Stream: Sell main stream electronics, jewelry and current trends. This is great because lots of people want it but on the flip side lots of people are selling them. The Ipods, Iphones, Blue Tooth Headsets etc. There are rare circumstances that change this type of sale like the Wii. Where the manufacturer sells on limited release and only people with the knowledge to keep track of retail shipping schedules and grab one get them. The the resale on the net is huge. A $249 Wii sells on average for $320. After fee's its a quick and easy $50.

2)Niche Marketing: Selling items that are not sold many places but have a demand. Finding a niche market can be hard. This requires alot of research into products availability and demand. Some companies offer this research at a price. Depending on were you are in available capital the do it yourself method is a good way to start. Funny things like Zebra rugs and Yoga Accessories are strong niche market products. Not alot of places sell them but they are in demand. A niche market is a fast paced sales style. Usually once a hand full of people see the increase in demand for a product they follow suit and sell the same.