.CO domains are available for a cheap price of $27.99 and for your information, one of the first companies to snatch a .co domain is twitter – i.e. their URL shortening service, which t.co.
One of the biggest advantages of the .co TLDs, besides the fact that they’re similar to .com TLDs, is the fact that they are already widely recognized, as more than 20 countries, including the UK (.co.uk) and Japan (.co.jp), already use them for their country specific domains (via).