At the excellent Geek Etiquette, we find some tips on the length and information you put in your .sig (email signature) file. I've been an Internet regular since 1996, when I first got to college, and my first .sig had my dorm address in it. To celebrate my Icelandic heritage, it also had a cute little Viking ASCII picture, that looked something like the following:
(____) o o --m----m--
Fun huh? Up until recently, my personal .signature file had two dashes followed by a space, a carriage return, then just my full name and my website URL. (My work one has my work IM info in it as well.) Now I'm signatureless, that, my email program of choice defaults to "none" as the signature, and for my best friends I don't 'sign' emails at all and for others I sign off with my initials, RE (I freely admit to copying Darren in that respect). Signatures of others are only ever clever or interesting the first few times we email, otherwise it's pointless.