If your windshield breaks -- not just chips, but actually breaks -- you know you really can't drive the car until the windshield is replaced. But a side window might not seem like such an issue, especially with all the cars you've seen with a garbage bag duct-taped over what's clearly a broken pane, right?
It's not that simple. A broken car window poses a few problems when you drive that can affect the safety of you and your passengers. While driving with a chip or scratch is fine, you really should have a car with a broken window towed to the auto glass repair place. Yes, sometimes this isn't possible given your situation, but if at all possible, towing is better. Otherwise, you have to deal with effects that make driving very unpleasant.
Taping plastic over the gaping hole that once held a window pane might protect the inside of the car on a sunny, cool day when you're able to drive slowly. But on a hot day, it doesn't really keep out the heat, and that makes it harder to cool the car with the air conditioner; in heavy rain, the tape could still allow a small amount of rain to leak in if the force of the rain hitting the tape causes a gap to open up.
Cleaning up window glass, even if it's tempered and designed to break into larger chunks, can be difficult. You can still end up with tiny slivers that hide in seat crevices. This is possibly the worst part because, while you can clean up large pieces easily and use a vacuum to get smaller pieces, the tiny shards seem to multiply on their own. It does help if you can clean up the glass you see before having the car towed, however, because you won't have to worry about pieces sliding under seats and into areas where there was no glass before. Pick up large pieces with gloved hands and use something like soft, fresh bread to get smaller pieces. Take a very fresh, soft slice of white bread and carefully press it onto the glass; the glass will stick to the bread (again, you need really soft slices for this because softer bread has that "sticky" quality that you don't find in dry, older bread). If you resort to using a vacuum, change the bag (with gloved hands) immediately.
One more issue that driving with a broken window brings up is the possibility of more damage. Let's say you have a window that's partially broken, with some of the glass still in place. If you cover the glass with plastic and try to drive to the glass replacement shop, and you hit a rough patch of road or a pothole, more of the glass could break off, and that is very dangerous when driving.
If you have to bring your car in to get the glass replaced, try to have it towed in. Check with your insurance company about coverage, or if you have roadside assistance through a credit card, see if that service will cover the cost. If you belong to an auto club, you should be able to get free towing up to a certain number of miles.