How to template'ize variable NAMES, not types?

Template parameters are restricted to types, integer constants, pointers/references to functions or objects with external linkage and member pointers -- but no identifiers.

But you could use a member pointer as template parameter:

template<int MyClass::* MemPtr>
void doSomething(std::vector<MyClass> & all) {
   for( i=0; i < all.size(); i++)
      (all[i].*MemPtr)++;
}

:

doSomething<&MyClass::aaa>(all);

Note that I changed the doSomething function to take a reference instead of accepting the vector by value.

sellibitze's solution is fine (though to be honest not very: see my edit), only it limits you to using only members of type int. A more general solution would be this (although the member is NOT a template parameter here)

#include <vector>

struct MyClass
{
   int i;
   char c;
};

template <class T>
void DoSomething(std::vector<MyClass>& all, T MyClass::* MemPtr)
{ 
   for(std::vector<MyClass>::size_type i = 0; i < all.size(); ++i)
      (all[i].*MemPtr)++;
}

int main()
{
   std::vector<MyClass> all;
   DoSomething(all, &MyClass::i);
   DoSomething(all, &MyClass::c);
}

EDIT: Also please note that it is not generally a good idea for a pointer to member to be a template parameter inasmuch as only such pointers that are known compile-time can be passed, that is you can't determine the pointer runtime and then pass it as a template param.