Sites that offer free Bitcoins for doing things such as surfing the web or posting to Facebook. However, these sites often make very small payouts. The way the Bitcoin fees are structured if you try to combine many small payments into a larger payment you may trigger fees that are greater than the total amount sent! Be prepared to put the small payments away for a long time until they are worth enough to buy something with it.
These payments are often called “dust” transactions. The fees in Bitcoin are mostly based on the amount of data it takes for the transaction. Combining these dust transactions creates so much data that the fees can exceed the value of the transaction. There are ways to recover the dust transactions. One easy way is to send larger amounts the wallet and then combine the dust with a larger transaction. Bitcoin armory wallet in expert mode has a “coin control” option that allows this. However, since these transactions are often worth less than 1 cent it is often not worth the trouble. Hang on to your wallet because you never know how things will change in the future.