I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions.

What permissions are need to be used on /var/www so that...

1. Source control like git or svn
2. Normal users in a group like "websites" or added to "www-data"
3. Servers like apache or lighthttpd
4. And PHP/Perl/Ruby

can all read, create, and run files there?

If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www. Therefore, it seems like the correct permission would be chmod -R 1660 which would make

1. all files shareable by these four entities
2. all files non-executable by mistake
3. block everyone else from the directory entirely
4. set the permission mode to "sticky" for all future files

Is this correct?

Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be.