Did you ever want to underline something in a mail, but without sending one of those disgusting HTML mails? Or do you want to be able to send underlined text in a chat system that won't let you? Well, there's a trick that often lets you post underlined text anyway: Unicode has an underline character that overlays normal characters. Enter some text here and see the Unicode-underlined form below:
(output goes here)
Hint: This e.g. works with plaintext mails (at least in Google Mail and mutt) and on IRC (even in +c-channels).
Have fun (and don't spam +c channels in IRC with underlined text).