As the title says, the tethered jailbreak for IOS 5.1 has been released for iPad1 owners. Since those devices are pwned for life, tethered jailbreaks are easy-peasey
However, iBooks users should note that, once again, Apple has fiddled with the protection around iBooks and so it won't work with the new 5.1 JB just yet. There are likely to be other incompatibilities too! Don't expect all 5.0.1 tweaks to work on 5.1. It has more changes under the covers than it appears
The usual threads have been updated -
Jailbreaking Methods for the iPad
TUTORIAL - Jailbreak iPad1 on IOS5 using redsn0w
Happy Hacking fellow iPad1 owners.
And before you ask, no, there won't be a jailbreak for the iPad2 or iPad3 for quite a while yet..., and neither is an untether for the iPad1 on 5.1 likely any time soon