TLD whois servers

We're in the process of putting together a free tools and resources site for general use of this community. Amongst the things we're putting up (ping and traceroute gateways, looking glass machines, etc) is a smart whois front end that will allow a user to enter a domain name with any tld. The problem is that IANA does not currently require a tld manager/administrator to provide the address of their whois server. In some cases, apparently, there may not even be a whois server. Does anyone have a partial list that we can incorporate, or pointers to resources? We hope to have a useful functioning site by NANOG in Atlanta. /rlj