MTurk is pretty popular.
MTurk is a product of Amazon.com. After you sign up you can choose from several ways to earn money.
Some of them are mundane, some a pretty quick. I actually enjoy some of the surveys, the ones from colleges that test reflexes or facial memory, so its not always a hard gig.
The tasks you do are called "HITs" and there are several different HITs you can complete.
Google searching key words - Basically, they give you a phrase to search for and you record what page you found it on and you copy and paste a sentence from the website to prove you found it.
I can usually do 3 HITs every 5 minutes. This usually pays $0.10 per HIT.
Surveys - These are just like any other website. Some surveys take 10 seconds and some take 10 minutes.
Most HITs pay between $0.25- $0.75
Write short essay or review - These can pay really well if you enjoy writing. Sometimes these are "invite only" but can pay $15-$20 a HIT.
Voice mail transcribe - Pretty much what it say, you listen to a voice mail and type out what it says.
(MAYBE 15 minutes a day, just testing the waters)
(Some examples of some HITs)
(Higher paying HITS)
Another really nice thing about MTurk is the community. There is a LARGE community that helps people get started and even provided lists of good paying HITs. I will be writing later on more MTurk information and provide several more links to get you started.
For now though, here is where to start:
MTurk
10 Helpful tips to get started
Turkernation