Also note that there's a big difference between installing a custom ROM on an Android phone, and just rooting it. Custom ROMs may offer plenty of features that aren't available direct from the manufacturer, but most of them can be added to a rooted phone by simply installing the right apps. That's what we're after today.
If you haven't rooted your phone yet, but would like to know more about the process, be sure to check out our comprehensive guide to rooting Android phones.
Superuser is the first app a user should install after rooting, if the rooting method didn't do it already. "Rooting" a phone allows a user to establish total control over the device, but Superuser is the app that provides the button for that control. With Superuser installed, any app that needs root privileges to run will have to ask permission, and an informative pop-up will display with the option to give it those privileges. This app is an absolute must for any of the other apps on the list to even run.
Titanium Backup is an enormously useful app. Not only can it backup apps, but it can backup apps and all their data, and it can delete apps — even system apps or bloatware. Making regular backups of all your apps (and their data) can ensure that if you ever really screw up, say in trying to install a custom ROM, that you can still have everything the way you left it should you need to wipe the entire phone and start from scratch. For more detailed information, see our full guide on using Titanium Backup.
It's a sad fact that Android ships with no way to take screenshots. ShootMe is an extremely simple, user-friendly app that rectifies that situation, but it needs the phone to be rooted first. ShootMe's greatest feature is that it allows you to choose from several options in deciding what the trigger should be for the screenshot to take place — whether it's shaking the phone, covering the light sensor, or just yelling at it (my favourite).
Metamorph is a small app that allows you to theme any part of Android by applying simple patch files. Learning how to make your own themes isn't exactly the easiest thing in the world, but most users don't bother — there are plenty to choose from, made by other users who are absolutely nuts about theming. Parts of the system that can be themed by Metamorph include the lockscreen, menu screens, individual apps, or just about anything else that's ever displayed on the screen. It's all possible.
Adfree may actually be the greatest root-essential app available on Android, and it's one that you never see unless it needs updating. All Adfree does is block ads, but it does it for everything on the phone. Since the app works by blocking ad-serving sites at the IP address level (by modifying the phone's Hosts file), it doesn't slow your system down, and it does a remarkably good job. Even if you don't mind ads in your browser, using Adfree makes "free" apps from the Market much more tolerable, since most of them have pop-up ads that tend to ruin the experience otherwise.
Recently mentioned SSH Tunnel is an app that allows an Android phone to connect to the internet using an ssh tunnel for a completely secure connection. It's great for those times when you've got no data signal, stuck at work or a coffee shop that only has public Wi-Fi available, and you need to be sure that nobody is snooping your sensitive personal information as you connect to sites like Gmail or Facebook.
Tasker (Root adds features)
Tasker by itself doesn't require root privileges to run, but some of its more impressive features do. Giving Tasker room to do what it does best is definitely a good thing, since it can practically automate your entire phone given the right amount of power. Rooting your phone is the only way to give it that kind of access.
SetCPU has been, is still, and will probably be for quite some time the de facto tool for controlling a rooted Android phone's processor speed. SetCPU allows the user to exert total control over how fast, or slow, the processor runs at any given point in time. As an example, SetCPU can force the processor to sit at its lowest setting whenever the screen is turned off, but to use a range between 240MHz and 806MHz as needed while the phone is awake. For phones that have the ability to drastically overclock, SetCPU can help ensure that they don't overheat by keeping watch on the temperature, and acting accordingly. Overclocking or not, battery savings and overall performance can be greatly enhanced using this app.
Busybox is often called "the Swiss Army Knife of Embedded Linux", because that's what it basically is. It's not an actual app that you run, but instead provides all the Linux/UNIX commands that we know and love. Without the commands installed, the barebones "Linux" that Android runs on top of can't really do too much, making apps like Terminal Emulator nearly worthless.
Finally, Wireless Tether. For many users, this feature is the single most important thing in the world of mobile devices, so having the ability to use it is a must. Wireless Tether turns an Android phone, regardless of carrier, into a full blown W-Fi hotspot for any nearby devices that need one. It's as simple as that, but only rooted phones can use it.
There are plenty of other apps out there that only work with rooted phones, and it doesn't seem likely that the carriers are ever going to allow phones on their networks to sell with root capabilities baked in. If you want the added functionality of these apps, there's just no way around it. You've got to go rooted. So, if you're convinced, head over to the rooting guide to see what's required to set your phone free.
Know of any other great apps for rooted Android phones? Have a personal favourite that's not on the list? Share them in the comments!