Long car trips.

In a season where many have to visit their families, regardless of whether they actually want to, there can be many long car trips.
These can be tedious and horrible, especially if you're in the car with other people.
So here's some benign ideas for the car.

Are we there yet?
This simple little question is one of the age-old enjoyments of children in the backseats of cars. However, at best, it's probably only worth about 10 minutes of entertainment, 20 if you can repeat it in different languages.
Simply switching up some of the pronouns can make this little question fun for everyone.
"Am I there yet?" when people answer you, tell them you weren't asking them. Repeat this to yourself as many times as you want.
"Is it here yet?" Just look fearful and don't answer people when you repeat this. If they really pump you for an answer, leave it cryptic ("You don't know?"). Only claim that it has arrived if either the sun rises or sets during your drive. Make sure you repeatedly cross yourself. "Are they here yet?" also works.
"Is she/he there yet?" point at other cars.
"Is she/he here yet?" point at someone in the car.
"Are you there yet?" This works primarily as a driver's retort to "Are we there yet?" confusing only for small children really. "We can't get there until you do, so think faster".

Rest areas
Only one option really. Order one thing from every crappy sub-standard chain in the rest area and host a rest area iron chef. Extra points for the person who can think of a desert that doesn't involve Cinnabon. Wait a half an hour after eating so the car doesn't fill up with the fartness.
Don't do this if you are only traveling with a signifigant other. Use this time to become members of the 34 1/2 miles down the highway club. Works best at campsites. Not reccomended for those with motion sickness.

Games/INB's
If you are alone, give yourself 5 points for every second of eye contact you can have with someone in another car without them speeding up/slowing down to avoid you. Do NOT follow them for another round, the beauty of this game is that it is vaguely unsettling without involving police interaction.
Got children? Dress them up like dogs and have them stick their heads out the window. Have them bark at other dogs. Or just get a friend to do it. Large hairy gamer nerd types work well with this.
Try to get in a conversation with SUV drivers or truckers about why their car or truck needs to be so tall. Play psychiatrist with them on this one. If you have one too, turn it into more of a support group feel.
Write non-existent sport's teams names on your car with spirit foam. "GO BLENDERS!" Combine two old school car pranks into one epic one: ghost ride the chinese fire drill.

That's all I got for now. I might extend this list on the later.