Just a couple of days after the anticipated release, the Circle of Eight forums has news of the
Keep on the Borderlands conversion for
ToEE demo release.
There are some important installation instructions, you'll need Microsoft's .Net 2.0 installed and a patch has already been released, so head over for the full details and download links (~300Mb).
If you want to jump straight in, the mod is being hosted at
ModDB and
Filefront.
More information.