Reclaim snatched domain name
Firstly,
All of these questions should really be addressed to your domain registrar.
That said:
1. How can I get hold of the new registrator (My contact information still appears in the whois databases)?
If that's true, then it would appear that your domain name was not actually fully expired. When a domain is expired the old whois information should be purged, and then when it's re-registered by someone else the new details should then be present.
Without knowing at least which TLD it's in (and maybe the whole name) it's hard to guess more.
It's possible that the domain registry has themselves pointed your NS records at their own link farming pages.
2. Is it possible to appeal to any authority to claim ownership?
Talk to your registrar, and if necessary the TLD domain registry. What they do will depend on the TLD's policies though.
3. Is it possible to contact google about removing the page from the search engines?
No, as far as I know Google will not arbitrate in cases like this - as far as they're concerned the new content is legitimate and there's no reason not to index it.
If it's a .com domain and it's literally just expired, it's possible the domain is in "Redemption".
This is a last-chance status before the domain is deleted where the domain remains registered for approx 1 month. In this status it's also very likely the registrar will put pay-per-click adverts in place of your website...
Contact your registrar for advice!
Sean
If your domain name just expired, it's more than likely that you have some kind of renewal grace period. Also, it's not uncommon for expired domain names to revert to a parking page. Contact your registrar, and see what options are available for you.
Otherwise, if you have an objective trademark right to the domain name, that usually helps you retrieve it with minimal resistance.
If all else fails, you can turn to the UDRP process (Uniform Domain-Name Dispute-Resolution Policy). There's a fee upwards of $1000.00 associated with this, charged to both parties involved. So try your other options first.