A drug which has several mental performance-enhancing effects similar to stimulants, but isn't quite a stimulant. The chemical itself was first synthesized in the 1970s by a French pharmaceutical company.
Basically, it keeps you awake and alert without making you jittery or "stimmed out". What's unique about it is that you can use it to stay awake for 72 hours, then sleep 8 hours, then stay up for 72 again with no negative effects. It does not suppress appetite or cause a "crash" like most other stimulants do.
It was intruduced in the US in the early 1990s, and since then has mainly been prescribed as an anti-narcoleptic. Recently, however, a lot of other interesting effects have come to light. Not only does it keep you up but it makes your memory and mental performance better, and can even be used to treat cocaine addiction. It's been prescribed for things like ADD and depression as well.
It's been reported in the NY Times that the US military (and probably others) have been working with modafinil. Not really big news-- the military has been using stimulants for quite a while.
There has been some talk of even making it over the counter, since it is pretty much not addictive whatsoever.
In the US it comes in 100mg and 200mg tablets.
They can be insufflated (snorted) to some effect but the pills contain a lot of different fillers so it's not really recommended (yes I've tried it a couple times). If you get them, don't expect it to feel like you're coked up, it's not very useful recreationally.