1. Does anyone know of a search site that will search by number of characters?
... like "any 4 letters", "any 4 letters including a dash", "any 5 letters", etc...

2. what website has the most domain names for sale? Not ones available through icann registrars, but ones people own but have listed for sale.

Thanks!

Can't help you on #1.

But, on question #2, I have found these two have extensive listings.

Buy Premium Domain Names, Domain Name Registration, Web Hosting (http://www.buydomains.com/)

GreatDomains.com - Buy and Sell Secondary Market Premium Domain Names (http://www.greatdomains.com/)

Thanks, Ruby. I'll check those out.

I found a "sort of" answer to #1. GoDaddy has domains for sale where you can advanced search for domains with no more than X characters... but this is aftermarket sales. Sales of expired domains they've bought up as well as sales by individuals... not domains available via any registrar.