Second Life is an immersive 3D world, in which you can actually build, program, and even sell your own totally customizable objects. Second Life has a virtual currency called the L$ (Linden dollar) which can be exchanged for real money.
Since there are no fees taken out of any transactions within Second Life (there are only fees when you exchange your L$ for real currency), that makes Second Life one of the only feasible ways I know of to collect microdonations via the internet, and a better payment method than PayPal.
As of 1/4/2011, I find the newest official Second Life viewer to have a really terrible, confusing interface in comparison to the old versions, and search doesn't work anywhere near as well.
Thank goodness, it's still possible to use an old official Second Life viewer - Version 1.23, which can be downloaded at Second Life's official wiki: http://wiki.secondlife.com/wiki/Linden_Lab_Official:Alternate_Viewers#Viewer_1.23
This section of my site might someday feature many more things. For now, though, there's not much here.
- MagnaMural: Texture Display & Organizer - A scripted item I wrote in Second Life. It was originally a commercial product but I released it into the public domain.
- LSL Scripting - Downloadable Wiki Mirror 7-7-7 - A downloadable copy of the LSL Wiki. From 7/7/07, but still very useful and much nicer than having to always be on the internet to browse some of the best documentation of LSL available.
- Entropia Universe - As of 1/4/2011, I actually can't even use Entropia Universe anymore, because my computer doesn't meet the minimum requirements to run the software. So, my comments below are about Entropia Universe as it was a couple years ago.
Old text written sometime before 1/23/2009: Also free, but, this is more like a standard online adventure game where you can't easily create new content, and you go around killing monsters (or more likely, just running from them if you're a non-paying player). It, too, has a virtual currency, but, the $100 minimum withdrawal and $10 fee makes this not very feasible as a payment method, and, as a non-paying player, I have found it is quite hard to make money.
However, the graphics are really nice. Even just hiding the on-screen controls, walking around and taking pictures with the Fraps software (linked to below) is fun. The world is absolutely huge, and it's rather gratifying to go sightseeing. By the way, it's a good idea to take your time to design an avatar (since, unlike Second Life, you can't change your appearance at will).
- Fraps - Computer Game Screenshot/Video Recording (Machinima) Software - This can be used to take screenshots and movies within Second Life and Entropia Universe by pressing a single key on your keyboard. The program has additional features if you pay $37, but it's excellent and very useful even if you can't afford that.
- OpenSim - Install and Configuration Tutorial - A wonderful tutorial which will tell you how to install OpenSim, a program which allows you to run your own Second Life server on your own computer.
- Second Inventory - A closed-source, commercial program, which I purchased so I can transfer at least some objects between Second Life and my own OpenSim.
LSL stands for Linden Scripting Language, which is used to create scripts in Second Life.
Other Virtual World Games
Only one on this list for now. I'm not usually interested in games like this unless they have a virtual currency and there's a way to make money from them.