Originally Posted by PornMD

.org if it's financial, health/medical, political, help/informational/resource or of course charity/non-profit, .net if it's anything else. MAYBE .me, .co, .ly or .io for social. Don't bother with anything else - the other exts suck.

That said, if you're getting the domain for a primary brand for a business you want taken seriously, get a .com. Either find something different or fork out the $500. I paid $10,000 once for a domain I intended to develop, never did and sold it for $15,000. You're not just buying a name for a website but an asset as well, remember that.