mod_text2html is an Apache module which is designed to replace Apache's internal text/plain handler. It converts carriage returns into "BR" tags.
If it finds valid URLs it turns them into "A HREF" tags, and it does a good job of trying to not muddle up HTML that has been flagged as text. It converts commas and ampersands into HTML entities.
It uses the same method as the Unix find utility to determine if a file is text in the first place. If it determines that the file is not text it sends the file, but does so as application/octet-stream.