As prices start to become a little bit more affordable, 3D gaming is becoming an increasingly viable option.
The monitor needs for gamers are pretty straightforward. An LCD with fast refresh rates, low input lag and a decent resolution will more than satisfy. Of course price is always a factor, with more expensive monitors offering better colours and other handy features.
While not the newest feature, 3D capable gaming monitors are finally starting to drop in price and are becoming almost widespread. Most of the 3D gaming hardware out there is built around the NVIDIA 3DVision technology. Rather than the polarised glasses you love to hate from your local cinema, PC 3D uses active shutter glasses like 3D TVs. While this setup provides very usable 3D, the glasses are bulky, need to be charged and are expensive.

You also need a special 120Hz monitor. If you have a Radeon GPU your 3D options are rather more limited, with no dedicated hardware available. There are some suitable third party 3D glasses and monitors available (as well as compatibility with some 3D TVs), but it will be some time yet before they are commonly available.
While it needs specific hardware, 3D gaming is pretty simple. Alternating frames from slightly different perspectives are displayed on your screen at 120Hz. A signal is sent via IR to your 3D glasses, which uses active LCD shutters to make sure each eye can only see one set of the alternating frames. This means each eye sees a slightly different viewpoint at 60Hz and your brain combines this into a single 3D image. Unlike cinema 3D glasses, there is little leakage of images between each eye, making the 3D more defined.
Since your 3D card already calculates and renders a 3D world, it’s not much extra effort to render it from the differing viewpoints and little slowdown occurs. You are limited to a maximum of 60fps in 3D mode though, and since the 3D glasses block some light you might need to up the monitor brightness.