JailbreakMe

JailbreakMe is a site that has been used multiple times to jailbreak iDevices. It is currently online, hosting the Star and Saffron jailbreaks.

First Incarnation (AppSnapp)
Initially, Conceited Software utilized the LibTiff exploit with jailbreakme.com, which also went by the name "AppSnapp," to jailbreak iOS 1.1.1. Upon the release of iOS 2.0 and the debut of the App Store, Conceited Software closed JailbreakMe, when it remained dormant for a while.

Second Incarnation (Star)
comex has since repurposed the domain for Star, his userland jailbreak for iOS 3.1.2 through 4.0.1. However, comex stated that the bug used for the untethered jailbreak was there until 4.3 as Apple did not patch the bug correctly. It was properly patched on 4.3.1 in order to prevent the jailbreak of the iPad 2. It's still possible the site could be repurposed to jailbreak iDevices up to 4.3, but this has not yet been done.

Third Incarnation (Saffron)
In June 2011, comex began to put up teasers on JailbreakMe. In early July 2011, someone Googled comex's other site and found a prerelease version of "Saffron," the third incarnation of JailbreakMe. Word about this "leak" inevitably spread. On 6 July 2011, "Saffron" made its official debut on JailbreakMe.

Owner Problem
On 7 October 2011, MuscleNerd announced that the domain was sold and that the new owner was unknown, so that there is a big danger of the site hosting malware. It turned out that the new owner was friendly and sold it the next day to Saurik who hosted the site anyway. Problem solved.

Certificate problem
Starting early December 2015, the domain started to display a blank homepage. In addition, JailbreakMe began to redirect traffic to HTTPS; however, the TLS certificate it was using was invalid. Turns out comex moved the files to his personal domain.

Forth Incarnation (iOS 9.2-9.3.3 semi-untether)
Luca Todesco released his own "JailbreakMe" to fix the 7-day enterprise certificate problem related to the IPAs that are used to rejailbreak the device after a reboot on the iOS 9.2 - 9.3.3 semi-untethered jailbreak. This is located at jbme.qwertyoruiop.com, and uses the Trident exploit chain to rejailbreak the device through Safari.

However, this "JailbreakMe" is totally unrelated to all of the above ones, and is different from the point of view that this will only rejailbreak the device after a reboot, and will not jailbreak it to start with.