LastPass is clearly the juggernaut here, and for good reason. The service was one of the first well-rounded password managers available, and one of the first that really made it easy to store all of your passwords either online and synced with other computers and devices, or locally on one device. In short, LastPass remembers your passwords so you don't have to, and makes it easy to audit your passwords, use stronger passwords in general, and even automatically change a password for you if a service has been hacked or compromised. LastPass supports two-factor authentication for your password vault using Google Authenticator, USB devices (using a method we've outlined before), or a YubiKey, The service picked up a much-needed update a year or so ago to streamline the UI and make it easier to use, and sports a number of additional features like credit monitoring, secure password and document storage (and sharing), notifications when a site you have an account with has been hacked, tools to autofill forms and streamline online shopping, and more. LastPass supports Windows, OS X, Linux, Android, iOS, Windows Phone, and Blackberry, and has plugins for Chrome, Firefox, Safari, Opera, and Internet Explorer. It's free to download and use, but if you want its best features and the mobile apps, you'll need to upgrade to LastPass Premium, at $12/yr.
LastPass' nomination thread was huge, with many of you showing your support for the app because it's made securing your online life easier in some shape or form. Many of you explained that you use LastPass so you don't use the same password on every site (which you absolutely shouldn't do), or so you don't have to write down passwords and risk losing them in a disaster, misplacing them, or accidentally letting someone else get a hold of them. Many of you praised LastPass' own security for keeping your data safe, and for—that one time they thought they may have been hacked—promptly locking everyone's data down, making sure they were in the clear, and encouraging users to take additional steps to protect themselves. If you want to learn more about LastPass, they stopped by to tell us the story behind the app not too long ago, and you can read their nomination thread here.