It really depends on what you want to do to get paid, as well as how dedicated you'd be in performing the site's tasks. Different sites can be split into different categories depending on the tasks the member needs to perform in order to get paid.
FusionCash, CashCrate, SwagBucks, etc. are what are considered to be GPT sites or Get Paid To sites. These sites offer a variety of different tasks each with varying rewards for each completed task. That's why the category is sort-of left hanging as in it begs the question "Get paid to do what?"; you can get paid to do much of any type of task, from completing surveys to joining a different website. The benefits of these type of sites it that it is fairly easy to make money since there are such a large variety of tasks to complete to get paid. The negative is that some of the tasks (and unfortunately it seems like the really high-paying tasks) want you to join a paid-membership using a credit card; even if the site offers a free-trial membership, most people fail to cancel their membership in time and end up paying for the membership (at least for one month) which is usually more than what the person made by completing the offer.
Then there are PTC sites; Paid To Click sites like ClickSense and NeoBux (2 of the most successful, long-lasting of these sites) pay their members to click on an ad on their site which will open up a new browser window / frame for the site that the ad was for, and the member has to view this new site for a set amount of time (usually several seconds up to a minute, but not much longer than that). The benefit is that it is again very easy to complete the task, but the problem with sites like this is that the pay is very low (some sites offer a fraction of a cent up to a whole penny for viewing a site for 30 seconds, or $1.20 / hour).
Some sites are strictly for completing surveys. Although survey sites like Opinion Outpost, Toluna, MySurvey, and Pinecone Research offer much better pay for the amount of time to complete the survey, they too are plagued by the same main problem that FC's users face when trying to complete FC surveys: people will answer many "demographic" questions only to find out that they don't qualify for the rest of the questions (and hence won't get paid for their work). Some sites are better in this area, however. Some use FC's technique in giving a small "booby prize" when a person gets disqualified from finishing a survey as a way to make that time spent not completely worthless. Other sites do a much better job at matching the surveys to their members and only inviting members to a particular survey if it is likely that the person will be able to complete the survey.
Of course there is also the option to make your own money-making site. If you can perform a service on-line, there is probably a way to market it to get money out of it. The easiest type of site to start up and monetize are blogs. Blogs are basically a person writing about their own interests in order to help others. Since the blogs are about a particular topic, it then becomes more easy to place targeted ads on the blog in order to make money. For example, if someone where to create a tech blog about the latest gadgets coming out on the market, the blogger could monetize the blog by placing ads to Best Buy, Tiger Direct, and / or other stores more dedicated to techy gadgets.