Nemu64 is a fast, compatible, Nintendo 64 emulator that uses a very efficient and highly configurable plugin system.
Nemu 64 is compatible with a lot of the Nintendo 64 games and emulates most of the console's hardware functions. It uses DirectInput and Direct3D (and DirectSound), and so will run on almost any 3D-card enabled system.
A software mode is also available, but it's really slow.