.com - no restriction
.net - no restriction
.org - no restriction
.edu - must be a higher level (college) school accredited by one of the US recognized regional accreditation agency, or a recognized international accreditation agency, unless grandfathered in (some high schools have one, for example)
.gov - us government sites, unless grandfathered in (some state governments have one, for example)
.mil - us military sites
.int - international organizations created by treaty
I'm not familiar enough with all of the ccTLDs to give a comprehensive list, but know that some require a residence address in their specific country. Check with the registrar for each ccTLD for details.
For a easy to understand list of rules and extensions you may want to visit:
[webstreetstudios.com...]