It may sound silly to try to put DOS executables online, but try to think about it: they are usually very small, very fast, they can run on wide variety of platforms. Of course, there is problem with security. I tried to overcome it by allowing download of NetDOS executables only from trusted URLs. And there are specific applications (like Intranet), where security is not so much important, and where executables are being downloaded from the server all the time. And you should also consider, that ALL programs which you download from Internet, with exception of Java applets, are executables: if you run them, you already decided to trust their authors. Executing programs is anyway hazardous only in single-user system, like plain DOS; if you are running some DOS emulator (like DOSEMU under Linux), it can be configured to be as secure as Java virtual machine.
I choosed following MIME types for *.EXE and *.COM file:
application/x-netdos-exe and application/x-netdos-com.
Suggested file extensions on server side are .netdos-exe and .netdos-com. Simple .exe or .com would be misleading, as normal DOS programs are not expected to be executed after finishing download.
You can try NetDOS scheme by downloading several short (4KB) ASM demos from NetDOS homepage (but only if you are online).