FreeBSD 8.1 BETA1 is available for downloading on (most of) the mirrors, as mentioned on the FreeBSD Stable Mailinglist:
The first of the test builds for the FreeBSD 8.1 release cycle is now available for amd64, i386, ia64, powerpc, pc98, and sparc64 architectures. Files suitable for creating installation media or doing FTP based installs through the network should be on most of the FreeBSD mirror sites by now.
For those who cannot wait, this is the link: http://ftp.freebsd.org/pub/FreeBSD/ISO-IMAGES-i386/8.1/
You can change the link to a mirror closer to you by adding your country code, e.g. http://ftp.dk.freebsd.org/ etc etc