Fiddling through the different types of limited slip differentials can be a tiresome task and there are a lot of terms which are pretty vaguely used on the internet. We did a differential 101 writeup while ago, and it is very on topic now that the season has started.
"Limited Slip Differentials (LSDs) are made in a few major types which are clutch-, torsen/gear-, viscous- and spool types. There are a lot of variants, but now we'll go through the basic differences in these types. An open differential is found on most cars from the factory, allthough some sport models have a factory equipped lsd."
Check out the 101 writing about different types of locking differentials »» Differentials 101
The writeup covers different types of differentials including pictures of each type, and also covers where each type is most applicable and what their pros and cons are.
Oh, and by the way, we know what we sell =)
»» Locking differentials