I’m sorry to do this to you, but I recently came across not one but two long lists of good small games, any one of which you can start playing in seconds, any one of which you can blow thirty minutes on without breaking a sweat. Beware!
The first list I learned about through Kevin Kelly’s Cool Tools page. He was pitching Mark Hurst’s Good Experience site, and that’s how I came across Good Experience Games.
The other list is from a place called Cognitive Labs, which appears to be associated with Stanford: Free Cognitive Games from Cognitive Labs. It’s a weird, chaotic site dedicated to slowing down or reversing the cognitive effects of aging. The premise is that these games are good for your brain. I can testify that they are bad for your ability to go to bed at a reasonable time. Try out Vector Ball and Reverse Asteroids. Also I am specifically curious how long JMike can stay alive at the Impossible level on the type-fast-or-die Word Shoot game. If you’ve never seen JMike type, it is a wonder to behold.
Rambles Blog at Star Chamber 
thanks for the words. weird and chaotic better than somnolent and boring, i hope. but, we believe in continuous improvement…i noticed the url in the analytics and had to see starchamber.com. re: stanford, there have been a few published studies and several colloquia recently using the game software (note: not all of the games, the rest fit an editorial theme)
Took my first crack at Word Shoot. Tried the medium level just to get the hang of the interface and then I had a go at the impossible level:
Word score: 28100
Correct: 153
Missed: 12
Correct rate: 92%
Final score: 29020
I think I can do a little better but probably not a super lot better. I was banging away on the keyboard loudly enough to attract attention in the office. It’s a little distracting to have to hit the ‘Enter’ key after every word, since the words are so short.
I think my raw typing speed has gone down since my early 20s, but only a bit. I was in a contest in 1991 where I did a five-minute stretch at 134 words per minute and I think I can still hit 130+ for shorter periods.
OK, I got up to 34330 on the Impossible level.
This is one of those annoying games where you score higher by starting at a lower level — I started at Hard and got 87860 points. I am guessing that the super high scores on the list, if done by unaided humans, were from the easy start.