SEGA Saturn Emulators
The complexity of the console requires a complex emulator and as a result all require a relatively high-spec machine in order to run games, even if they run at all since none of the emulators are complete.
Below is a quick rundown of each of the most well known programs. All are Windows based and require DirectX. Any homepages for the emulators are included if they are still online.
Be sure to check the specifications required for each emulator. They are equally more difficult to configure and prone to crashing than others. Most of the emulators will also emulate the ST-V/Titan arcade board.
For good speed you generally need a high end Pentium 4 or Athlon but preferably a dual core x64 CPU and a fast DX9 video card such as a GeForce 8600. If these requirements seem excessive, then check out the hardware overview for the Saturn. There is much going on!
For the best Saturn experience on a PC I recommend the officially licensed USB controllers manufactured by RetroBit which can be easily found online.
Alternatives are SEGA's own USB controllers; the standard model and those created for the PS3. Also, the Microsoft Sidewinder control pads have the same number of buttons and are quality pads. All these are becoming rare so Ebay is a good place to look.
These all plug and play with modern versions of Windows.
SSF
Is regarded as the best Saturn emulator there is available at the moment and is frequently updated. It is the most complete and not too difficult to setup. It provides more faithful emulation and has plenty of options for tweaking.
It can be difficult to track since the author and supporting files are in Japanese.
I have excellent performance on my modest dual core Athlon 64 and Geforce 8600 running the 64-Bit Edition of XP.
Extra information in English can be found at http://evilboris.sonic-cult.net/SSF/
Homepage: http://www7a.biglobe.ne.jp/~phantasy/ssf/index.html
Satourne
Is an emulator that can play commercial games however there are fewer new releases made. It can be complicated to setup but offers many more options.
Homepage: http://www.satourne.consollection.com/
GiriGiri
Is another emu, only this one was purchased by SEGA to be used in their download service. Since then there have been free versions available.
It is not as complete as the others though improvements may have been made.
Cassini
Is a hack of GiriGiri and plays many games. It is faster than SSF and easier to setup but has less compatibility. It may very well be declared illegal.
BIOS Files
In order to play games you will require the Saturn BIOS image that relates to the game you wish to play eg. European or Japanese and the ST-V BIOS.
Search the net for these files...