I was trying to register for a freaking Yahoo email address, and I must have tried about 50 variations of 'leafschick' and 'leafsgirl' until I decided I'd have to go with some misspelling. Misspelling 'girl' as 'gurl' makes my skin crawl, so I took out the 'c' went with the last year the Leafs won the Cup, and finally had my email address. I've used leafschik1967 at any sports related website I sign up to. Every so often, I get someone asking me if I am 39 years old. I should start saying yes, since its less embarassing to be old than being a Leafs fan at some times.
On ebay, its 'hockey_chick_8' which is pretty unoriginal. Clearly ebay had less users than Yahoo, and I went with '8' which was my hockey number. I do believe that number has been officially retired in chat on HI as well.
I have other user names for other sites, depends on where I go. I kick around on a few military forums, where my handle is D_Plus_One since my birthday is June 7, which of course, is the day after D-Day.