Over on the Windows server blog, they've got an explanation about the build of Longhorn which has just been released, and will be available to Technet and MSDN subscribers after the Easter holidays. If you're not a technet or MSDN subscriber (shame on you) you can register in advance for the public beta
Between Betas we let out "Community Technology Preview" builds, CTPs are generally a month or two apart and the last CTP was in February. We've said things like "Longhorn is on track for Beta 3 in the first half of the year" or "in the next 90 days". Those who want to guess when Beta 3 will come out will be thinking that if was at the end of the Window we've given then there would be another CTP: but the Windows Server teams say "This marks the last CTP we will release before Beta 3", so it's nearer than that. Obviously there needs to be a breathing space after the CTP, but the Windows server blog post ends "Beta 3 is just around the corner!"
Release dates for the beta are being talked inside Microsoft and I can reveal that Beta 3 will