The N64 BIOS for MESS link above doesn't work. I've attached it here.
I use Mednafen for number of older consoles. I use real hardware when I can, but some folks forget to check their homebrew on real hardware (or can't check it) and it doesn't work except on emulators.
Stella is probably best for A2600 stuff.
No$gba might be a little better, but it's Windows. For Mac/nix folks,
DeSmuME is probably better.