I have never done this for my own personal gain, however,
I have helped a few people get started with drop shipping
for sites such as eBay, Craigslist, etc...
The one piece of advice I CAN give you is to be VERY careful
with whomever you choose to use as a supplier. If you have
funds available for testing, once you find a few drop shippers,
test them out by placing small orders and having them sent
to friends or family first. Make sure it is exactly what you're
expecting it to be (item condition, speed of delivery, accuracy,
etc...)
As with ANY business, you really have to do your research
first, before getting too involved.