NesterDC is a NES emulator for Sega Dreamcast started by Ken Friece, though it has now been taken over by Takayama Fumihiko. Its current version is 7.0 , which was released on October 23, 2002. NesterDC is very playable, as many games are full speed, with most others being very close. The sound emulation is excellent in most places, and NesterDC has many advanced features and supports many external NES devices.
Here are a few of NesterDC's features:
almost fullspeed emulation
sound emulation
extra sound emulation
optimized PPU emulation
FDS emulation (need disksys.rom)
normal NES save to VMU (with compression)
statesave to VMU (with compression)
statesave to Dreamcast memory (as temporary save)
game genie
4players game
autofire
NES reset
adjust Dreamcast's screen position
NesterDC supports the following peripherals for NES:
Family Keyboard (controlled by Dreamcast Keyboard)
Optical Gun (controlled by Dreamcast Controller, Dreamcast Mouse)
Space Shadow Gun (controlled by Dreamcast Controller, Dreamcast Mouse)
Hyper Shot (controlled by Dreamcast Controller)
Crazy Climber (controlled by Dreamcast Controller)
Microphone (controlled by Dreamcast Controller)
This project greatly expands the lifespan of your Dreamcast, by adding hundreds of classic games to its library. I highly recommend you give it a try, as it is an excellent piece of software.
Some information in this node comes from http://www.dcemulation.com