What exactly is 'other' as a traffic source? How else do they get to my site if its not via referral, search engine or direct?
Just did a quick search: http://marketingtechblog.com/email/other-traffic-source-google-analytics/ This site says it's most likely emails.
Other traffic means, visitors came from campaigns like email campaigns, banners or news letters (it means you tagged emails, banner and news letters with tagging use of Google URL tool builder) in fact you can also track your tweets with the help this URL builder.