For N64 just use a GameShark/Pro Action Replay and the hacked utilities so the driver works on non win9x systems.
Otherwise, unless you're willing to mod a dumper like the V64, Z64, of CD64 you'd need a 512Mb version of a v64jr. to dump almost all known titles. That said, some can only be successfully dumped with a GameShark/PAR.
In both cases the computer you use would need a parallel port. If you don't have one a USB->parallel adapter won't natively work with either, but there is a very slow driver now in development.