Other .blend formats?

There's a free 3d software called MeshLab which does a good job of converting various open-source file formats to all kinds of other file formats. Since .blend is the proprietary Blender scene file format, there aren't any other software packages out there that support it directly other than Blender itself. However, you could export any of the models to .OBJ, for example, and then use something like MeshLab to import that OBJ and convert it to .3ds or .ply or whatever format it can support (there are dozens). Keep in mind that .3ds is a very old file format that does have its limitations. I don't think it will support high poly objects at all. Anything over 60k polygons will not be supported using .3ds.