Leaving aside the possibility of brute-force DNS lookups, the only real way to do this would be to do a zone transfer from Dreamhost's nameservers, but I assume these transfers are restricted to allowed slave servers only.
"Secret" web sites can still become known though, if they're spidered by a search engine or appear in referral logs.
The real question is why does it matter? If you've got something sensitive on the web, password protect it, don't rely on luck to keep it secret.
If you want useful replies, ask smart questions.