I finally figured it out....
...does not work. it just shows a blank space
<singleline>Title of item</singleline>
Apparently, "Title" is a reserved keyword or something. Or there is just a bug in the templating language.
This should be a well documented issue, but there is no note of it on any of the main Campaign Monitor template tag pages. I can't tell you how many hours I've wasted bumping into this problem on previous campaigns.
Thanks for raising this with us, and sorry to hear you've been experiencing issues with your <singleline> tags.
Just to confirm however, 'Title' is not currently a reserved keyword, and should certainly display by default, and so would you mind dropping us a line at email@example.com with the name of your account, campaign and template you're working with, and we'll be happy to take a look and investigate further for you :)
Thanks for your patience and look forward to hearing from you!