On a GitHub wiki page, if I type:
www.foobar.com
GitHub automatically assumes this is a URL and makes the text a hyperlink to http://www.foobar
This isn't limited to wiki page, and is part of the GFM (GitHub Flavored Markdown) url autolinking feature.
Putting them in `` can work but display the url as a code: foo http://example.com
bar.
foo `http://example.com` bar
Another trick (mentioned in this gist) is
http://example.com
That will display http://example.com as regular text.
In your case (without the http://)
www.foobar.com
That would also display www.foobar.com as regular text.
geekley adds in the comments:
For emails, you can use
foo@example.com