What I usually do when I suffer from insomnia is I just play something I enjoy ( whatever that would be for you), but that doesn't stresses me too much. Try to find a game that really draws you in, but don't play it on hard, so you don't get frustrated. Also I try to avoid games that stress my eyes, so no narrow fov, too much flashing stuff and no small text as well as a game that preferable has voice over and doesn't require much reading at all.

I'm not sure if this is what you are looking for, but maybe something like Bejeweled or Plants vs. Zombies?

That reminds me, Amazon has a really cool Zombie Bowl O'Rama game for download. It's not free but it's got some really groovy albeit silly graphics and some great sound effects. It's nice and casual is the best part.

Any of the Civ/total war games

Good call on PvZ, it's one of my favourite games when I'm totally burned out.

Recently when I can't sleep I've been playing Might and Magic: Clash of Heroes. It's pretty to look at, easy to pick up and play, and its repetitive but satisfying turn-based gameplay never fails to make me nod out after a few late night bouts.

When I'm tired I generally play Rollercoaster Tycoon or Simcity 4,

Here's a few others I can recommend: The Longest Journey, Syberia, Civilization series, Uru, Tropico (any), Heroes of Might & Magic (any), Age of Wonders: Shadow Magic, Pharaoh, Zeus, Caesar 3, Ghost Master, Minecraft (on peaceful no enemies),

Really it depends what you like when you're tired... I am more into happy, colourful kinds of games rather than anything a bit grim and gritty and I don't mind finishing off my brain with something a little cereberal.

I usually fire up my console and play a few fighting games - preferably wrestling since it does not require very fast reflexes. It lends to a sense of a catharsis.

On the pc it is usually a tbs like HOMM or disciples since these games are visually appealing and soothing.

I can't play jack shit when I am tired.

No. it is usually my ps2.

I suggest this:

1) Obligations first or whatever tedious work needs to be done
2) Get sleep (more important than most people give it credit for)
3) Now you can play in peace

I can but it's the opposite of enjoyable. The only enjoyable thing to do when you're sleepy is to sleep and unless you got some must-do-nows on your current to-do list it should be priority 1.

Eufloria is actually a pretty good bet if you're mellow or tired.

Speaking of mellow, ever turn out the lights and watch the opening launch scene from Homeworld?

No, but now that you mention it, yeah that'd work:)

Wow, you're able to play point-and-click adventures when you're tired? For me it's quite the opposite; they make me sleepy after a while, especially when I'm a bit tired to begin with. Same as reading books. I don't mean to say they bore me - I love P&C - but all that reading and/or listening requires a lot more concentration than the simple 'pointing' and 'clicking' you'd have to do in an action RPG or some casual games. It's also more passive, and a bit closer to watching TV. P&C adventures are among the last games I'd play when I'm tired, unless I'm specifically looking for something that helps me fall asleep even faster. ;)