Domain names, especially .com based ones, are very hard to get. Domai.nr allows you to search for unconventional domain names like del.icio.us or blo.gs in case the .com variant is not available.
You enter a word or phrase, and Domai.nr would list for all possible combinations of domains. For example, a search for “cool domain” would list cooldoma.in, cooldom.ai/n, cooldo.ma/in and so on.
Note that Domai.nr itself is a domain hack.