I'm working on a project that requires crossplatform support.... Irrlicht supports that, but unfortunately I am unable to find an editor that meets that criteria.
My first option was to use irrEdit (since it is some what the de facto), but it only works on Windows.
The next viable solution is Blender, but I am wondering if there is a better alternative to irrEdit that has crossplatform compatibility.
As far as I've seen, there isn't really much an alternative to irrEdit, let alone a cross-platform one, aside from just using modeling software. It seems that many Irrlicht users just go ahead and use modeling software like Blender/3ds Max, so that's probably your best bet.
If you really need to edit your scene files (becaues that's what IrrEdit does) on another OS than Windoze you might take a look at the "Project Announcements" forum. I remember that some cross-platform scene editors float around there.