Full Review
Fiverr is one of the longest-running gig worker portal. The idea is simple, very simple. You create a profile and tell people what you can do. Buyers search and book your services. You get paid.
It is a great place to earn money, you can offer any service you can imagine. Personally I offer services as a ghost-writer and graphic editor, but there is a space for everything you can imagine on the site.
Nearly every customer on Fiverr is a pleasure to work with, but every now and again you will come across an annoying customer - luckily there is an option to cancel orders if you really can't stand the person you are working for!
The biggest problem is getting started. Nearly all orders go to established sellers - people just aren't interested ordering from 'newbees'. You may need to get friends and family to order from you a few times, and leave great reviews, before you get any 'real' customers. This is, of course, against the rules! If you are careful, (making sure that these 'fake' customers don't use your computer or credit cards etc) then there is no real way of Fiverr knowing, but be aware if you get caught - you will loose your account.
The other issue is the fees. Fiverr keeps around 30% of the payment (as a seller you will loose 20% of your earnings to fees and sellers will
pay an extra 10% on whatever you charge as another fee). On the other hand they have a HUGE number of users and it is worth it.

Above is a screenshot of my earnings from Fiverr. As you can see things are going pretty well! Fiverr is a place that you can actually earn a proper income online - it just takes a lot of patience at the start.
Pros
Very legitimate.
A place you can earn a significant income.
Cons
As a new user it is hard to attract new customers.
High fees.