In addition to the two mentioed above there are also Xing & Blade.
THis link will take you to an interesting bit of info about the 4 main encoders (these are found in a variety of programs - you'll have to read the small print to find out what encoder your program uses).
The BIG important answer is that if you're ripping to 320 then they are all pretty much the same - proecessing signal almost to 20Khz. As the you progress towards 128 or even lower they diverge - sometimes wildly: for example LAME encoded rippers ignore music above 16Khz if reducing to below 100kbs.
it seems the fatstest encoder - Blade - has some majot peaks AFTER its cut off point!
Ars Technica: Do MP3 Encoders Sound Different? - Page 2 - (3/2000)
In summary:
The envelop please:
Low bit rate winner (128 kbs):
Fraunhofer. It was no contest. While not CD quality, the FhG encoder was sonically the least offensive. And with its superior measurements, it clearly beat out the other encoders at 128 kbs. If you have a tiny hard drive or a portable MP3 player with only 32 MB of memory, this is the encoder to use.
High bit rate winners (192 and 256 kbs):
Fraunhofer, LAME, Blade, and Xing (in order of preference). At the higher bit rates they don’t all sound the same, but the encoders in general were very listenable. I found the Xing high frequency measurements a bit worrisome, but at 256 kbs I thought the Xing encoder sounded as good as the rest. If you are "Napsterizing" some music, I think 192 kbs is a good compromise between sound quality and download times. For my personal MP3 CD-R disks, I encode at 256 kbs. This is still more than 7 CDs on one CD-R.
