For a while now, my site has supported custom subdomains... meaning people could type whatever.milov.nl and end up here. Never did anything with it other than redirect all subdomains to the main site - until this morning that is, when I came up with these two uses:

Quick-jump to iambald-number:
Typing 1, 2, ... 112 as a subdomain opens the matching iambald-page. Example: 24.milov.nl, 100.milov.nl, 112.milov.nl.

Colour view:
Want to quickly test what a particular hex or rgb colour value looks like? Try ffcc99.milov.nl, 990000.milov.nl, rgb(51,153,153).milov.nl or any other colour value as subdomain. Providing a handy way to link to or even bookmark one's favourite colours.

Update: even shorter rgb syntax: 250,100,50.milov.nl