We have very few cPanel customers who have mod_mono installed and running. I'm not aware of any non-cPanel users who would have it installed but, of course, there is a chance that some are doing this.
If you have cPanel (I believe you do) mod_mono can be easily installed using either /scripts/easyapache Apache recompilation script or through WHM >> Software >> Apache Update - mono version can be selected on the additional options screen.
In general - if you have an ASP based site it would be better to host it on MS Windows system rather than try to relay on various emulators
Thanks for the reply. You answered my main question, should I do this...
I have a potential customer, but his site is all aspx. I don't think I want to rock the Linux boat because of one customer. Oh well.....
I would also see what kind of ASPX stuff they may want to be running. Are there PHP equivalents out there?
I had a client that wanted to move their site over, but they had an employee area written in .asp. However, what it was was essentially a document sharing area and a group calendar. I ended up introducing them to Google Apps, which ended up being much better than what they had already.
Anyways, my point is... Either you could find a way to get their aspx stuff to work, or there might be something else they could look at using, too.