Ken Smith made the following announcement on the FreeBSD Stable mailinglist with regards to the upcoming FreeBSD 8.1:

We are about a week away from starting code freeze for the 8.1-RELEASE release cycle. Since sometimes that means stable/8 gets a little less reliable due to higher than normal levels of developer activity I’ll adjust the branch to say it is 8.1-PRERELEASE now.

The target schedule for the release cycle is available here:

And the wiki page to track the current status of the release (started but not heavily used yet) is here:

The current target release date is July 9th, 2010. You can find these and other FreeBSD related dates in the FreeBSD Events Calendar.