Wikipedia says:

A domain hack is a domain name that suggests a word, phrase, or name when concatenating two or more adjacent levels of that domain. For example, http://grou.ps/, http://fold.it/, and http://goo.gl/ suggest the word groups, the phrase fold it and the name google, respectively. In this context, the word hack denotes a clever trick (as in programming), not an exploit or break-in (as in security).

There are already a few domain name search tools that aid in finding domain hacks:

• xona
• domaintyper
• domainhack.me

There appears to be an auction site for very popular domain hacks. A lot of the names have capitalization; as far as I know, domain name resolution is case insensitive, so this doesn't matter.

My impression of domain hacks is that the name has nothing to do with what the company or individual does. At best, it's a stretched metaphor. The only reason I have goggl.es is because it was the first word that popped into my head looking at the TLD list on namecheap that was available and not too expensive. If I had a tool that showed me a few different ideas, I bet I'd find one that I liked even more.

• internetbs - the API is designed with resellers in mind.
• namesilo - it's unclear to me who this API is designed for.
• dynadot - a nice looking API splash page! I didn't look at the content.

• wordlist on sourceforge - just a lot of words. in several forms.
• google zeitgeist - it's good to remember the word "zeitgeist". too bad these words were the popular ones from yesteryear.
• twitter - use this python library to get the text of the last 24 hours of tweets from a popular identity.
• google ngrams - a product of google books digitizing the world's libraries, they generated and have provided for public download the linguistic n-grams up to n=5. it would be simplest just to get the alphabetic 1-grams.
• raw html - provide the URL and scrape the visible text from the page.

• toy with buying domainha.xxx and domainha.cc
• speculate endlessly about whether the new gTLDs will make this obsolete