Windows/Mac: The high-flying Aerial screensaver is one of my favourite things about the 4th generation Apple TV. It looks so cool I often find myself watching it instead of catching up on my Netflix shows. Here's how to get it on your Mac or PC.

Hi Lifehacker, I've been trying to find a countdown screensaver for my exams for a while now but I just cannot seem to find a good one. Have you seen any good/cool live countdown screensavers for Windows?

Android: Daydream mode is an underutilised feature on Android, but Dashclock makes it much more useful. By adding Dashclock or other Daydream-compatible widgets to your Daydream screen, you can have an always-on display of all the information you want.

Remember screensavers? While their original purpose -- to avoid burn-in on monitors from long periods of use -- is no longer an issue, they can still be useful. Here are some screensavers that combine the fun and the functional.

Windows/Mac: Screenstagram is an attractive, cross-platform screensaver that displays the best of Instagram on your screen.

Mac: It's a little annoying when you're reading a long article (or just spacing out) and your computer cuts to the screensaver because you haven't touched the mouse in a while. Should I Sleep is an app that keeps your display from going to sleep as long as you're sitting in front of it, using facial recognition to detect your presence via the webcam.

Some employers have security policies that require mandatory password-protected screensavers after a minute or two of idle time. This can be extremely annoying since every time you take a phone call or jot down notes you have to login again. For a low-tech solution to this problem keep an analogue alarm clock on hand.

Windows: Many utilities, such as JkDefrag, jazz up their routine scans by presenting them as screensavers. Security Essentials Screensaver turns your computer idle time/screensaver activation into malware and virus scanning time.

Your best bet to protect your gear against theft is never leaving it unattended, but Lifehacker reader Time Pilot AKA explains how he uses a clever screensaver as a theft deterrent for his Kindle.

Windows only: Photo gallery application PhotoJoy turns your digital pictures into collages, desktop widgets or 3D screensavers with just a few clicks. It's the type of application that your mum would like.

Windows only: Tiny utility MonitorES pauses your media player, turns off your monitor and sets Google Talk to away whenever you lock your PC.

Eye-candy RSS reader/screensaver MappedUp plots the location of RSS items on a world map with a nice visual effect—so you can use the screensaver for more than just pictures. Once you've installed and enabled the screensaver—and stepped away long enough for the screensaver to show up—you'll see RSS items show up on the world map in little balloons indicating the origin of the news story. You can customise the items that show up by creating a free account and choosing feeds or tags to display—or add any of your own feeds.< MappedUp is a free download for Windows or Mac OS X only. If you want to learn something instead of reading the news, you can always use Wikipedia as your screensaver instead.

MappedUp

Windows only: MultiPhotoQuotes is a feature packed replacement for the basic My Pictures Slideshow screensaver included with Windows. If you're running a multi-monitor setup, your favourite feature in MultiPhotoQuotes will definitely be the support for your extra screen space. The basic My Pictures screensaver will only put one picture on a single screen at any given time, which even on a small multi-monitor setup leaves a lot of empty space. MultiPhotoQuotes fills the entire available screen space with a grid of photos. If you like a good quotable every now and then, you can keep the quotes feature on to randomly sprinkle quotes from the included quote books.

Macworld's Dan Frakes shows off his favourite screensavers for Mac OS X in this video clip and many (but not all) are free, including AlphaBabySaver, Big Time Screen Saver, Econ, and Euphoria. Hit the Macworld site to get the full list of recommended 'savers. Personally I'm a huge fan of the built-in Word of the Day 'saver on my Mac. Do you use screensavers any more? Which is your favourite? Let us know in the comments. Screen savers live!

Video tutorial weblog Tinkernut demonstrates how to create custom screensavers from your own collection of digital photos or videos. You'll need to download a couple of free apps to get started—namely Format Factory and WG-Screensaver Creator—and then it's simply a matter of plugging in the media you want to convert. Granted, most operating systems have a screensaver-from-folder feature for rolling your own photo screensavers, but this method does video and gives you more control over what you see. How To Create A Screensaver

Running a screensaver on multiple monitors can be a tricky affair. The default Windows screensavers work just fine with multiple monitors, but you didn't install dual 22" wide screens at your workstation to blow away your coworkers with the expansiveness of your scrolling marque text messages. Fortunately there are several solutions to dealing with the quirkiness of Windows and multi-monitor screensavers.

Wikipedia lovers, you can get a random page from the 'pedia to just show up automatically on your PC with the Wikipedia Screen Saver. Sometimes you get pretty empty pages in need of work, other times you learn something pithy and new without lifting a finger. Choose Wikipedia from the screen saver drop-down in Display Properties after you install it.

Windows only: Free application Shutdown Screensaver counts the seconds until it automatically shuts down your computer. When you run the screensaver, it immediately starts counting down from two minutes. When it hits zero, your computer shuts down. If you stop the screensaver before it hits zero, your computer doesn't shutdown. This isn't a screensaver you'd want to install on most computers, since it (unfortunately) doesn't have any options other than brute-force shutdown, but if you're responsible for a computer that you always forget to shut off, this one could come in handy. If it's too heavy handed for you, you may be better off getting more in tune with your PC's power options. As is this is a simple app that does what it says, but if you're aware of a similar alternative with more features, we're all ears in the comments. Shutdown Screensaver

An adventurous Flickr user dug up a file in Leopard's example developer documents called Twitterverse, a screensaver that displays your Twitter world in a circle of thumbnailed activity. To use Twitterverse, find the file (a quick Spotlight search for Twitterverse should do the trick), open your Desktop & Screen Saver preference pane, and then simply drag the Twitterverse.qtz file into the preview window of the Screen Saver preference pane. To get it downloading your friends' tweets, click the Options button, enter your username and password, and try it out. I had trouble seeing results (just a blank screen), but if you have more luck, the screensaver is eye-tastic! Twitterverse Quartz Composer