Sql Server and Visual Studio 2005 on Win64 for x64
If you have an x64 system running Win64 for x64 and are interested in running Sql Server 2005, be aware that the Sql Server Management Studio (Beta 2, October CTP, and December CTP) does not currently run under Win64 for x64. If my memory serves correctly, the Sql Server Management Studio should run within the WOW system when Sql Server 2005 hits beta 3 (at least that is what I was told the last time I asked). You can also use the Sql Server Management Studio from a 32 bit system to manage an x64 installation, but I haven't tried that.
Visual Studio 2005 does currently run under Win64 for x64, though your mileage with any specific build may vary.