It's mandatory voting in Australia, but you just need to turn up and mark your name off the list and you won't get hassled to vote. But I guess, once you're there....might as well vote.

And the fine for not voting is $50 or so, and the electoral commission will take most reasonable excuses and waive the fine if you don't make it.

So it's more like a, "come on guys, do your civic duty" kind of thing as opposed to MANDATORY, and 90-something percent of the voting population in Australia just rolls with it.

Bonus: At most polling places you can usually get a "democracy sausage" for a small donation to a local cause, so most people will wander in just for that.

Edit: voting is on a Saturday, so most people don't have to take time from work to vote. There are legislative provisions that say that employers have to allow people time to vote if they work Saturdays, and polling stations are open from 8am to 6pm, which generally allows a window of opportunity for most people to vote without disrupting their day too much.

There are also postal votes of course, which can be ordered via phone/letter/internet and sent to your address. You can fill them in and send them back early, so there's no real reason to not vote.