http://ajaxwhois.com/
Excellent domain search tool, ajaxified, and supports multiple (even configurable) extensions, probably not 100% reliable though if it relies on whois.
http://www.resellerclub.com/
Domain and hosting reseller program. Starts from $100 signup and prices drop as the total lifetime spending on the account increases. Interesting model, competitive pricing. Ability to resell.
https://www.instra.com/en/domain-names/tonga/to-domain-registration/to
The cheapest .to registration I could find, starting from $72 a year (2 year minimum).
http://www.nameroute.com/
NameRoute are a UK based domain registration company, sister to HostRoute, their hosting half. They're the cheapest registrar I could find for .ac and .io domains, $50 each.
http://www.za.net/
Free domain names (without DNS) on the .za.org and .za.net subdomains. Requests require human approval and so can take a few days. Interface is plain text to email, old school!
http://www.quinapalus.com/cgi-bin/match
A great little tool. Give it a vaguely regex like pattern and it'll give you a list of all the possible words. Want 5 letter words ending in me or be, gotcha! Great for domain name inspiration. Output is scripting friendly plain text. :-)
http://www.marcaria.com/domains/Albania/register-al-domains-albania.asp
Register .al domains for $140 for 2 years including trustee services. Best deal around as far as I can see, the net cost is $100.
http://domai.nr/
Search across all the funky domains, short domains, etc. Awesome, instant, domain search. :-)
