I know http:// https:// and byond: can be used to create click-able links in BYOND outputs. Are there any others?
I believe the irc:// telnet:// and ftp:// protocols are also supported.
In response to Nadrew
ftp doesn't seem to, but thanks for the other two.
Unless you depend on the default auto-linking, I wouldn't think this relates to or depends on on BYOND, really. Generally, the 'link protocols' a given computer can use is those it has properly configured on his specific system. They can then be invoked from a number of places in the system, including web browsers, like IE which BYOND uses for this stuff.