I just came across the official mono porting ASP.NET applications guide. If you're planning on doing a port, I'd suggest you give this guide some attention.
The guide has some real gems like the following:
Using MONO_IOMAP
On Unix systems, Mono supports an I/O compatibility mode which allows you to ignore the file name case when accessing files on disk. The mode also takes care of disk designators (e.g. c:). Enabling the translation carries, obviously, some performance penalty, but is a good way to get your application up and running quickly. To enable the compatibility mode, make sure your web server's (XSP's or Apache's) environment contains the MONO_IOMAP variable set to all:
MONO_IOMAP=all export MONO_IOMAP
If you're using mod_mono, put the following line in your virtual host config file:
MonoSetEnv MONO_IOMAP=all
Knowing about this would have saved me a good couple of hours on the BlogEngine.NET port!