> How many emulators exists and which is recommended?

The only emulator I know is softvms, which is ported to several systems.

> I'm not sure all use the same file format also.

All ports of softvms use the same format, a simple binary dump starting
at address 0.

> Does VMI is a raw binary format?

VMI is a special format containing information how to download the real
VMS file used by Dreamcast browser.

> What are the different ways to test programs on a real VMS (I keep
> saying VMS, sorry :), also?

1. Download from the web with a Dreamcast.
2. Use a nexus memory card, dci utils and copy the data to a real VMS with
a Dreamcast.
3. Build a complex hardware called SerialToVM.
4. Build a simple hardware called VMU2PC.

For URLs about anything mentioned above look at the egroups page in the link
section.

Soeren