Jade previously blogged about a MXD to AXL converter script, which is a great tool that I use all the time. We also recently discovered the ”GDK ArcTools” script which enables you to convert the other way – AXL to MXD. While it isn’t perfect, it saves a lot of time by setting all of your data paths, layer names, max and min scales, and successfully converting simple symbology, such as solid fill polygons, and basic points and lines. Value map rendering, grouped layers, raster marker symbols, and labels usually need to be redone or tweaked, but if you are dealing with a lot of data it can be a great start.