"That" is used for identifying information. "Which" is for giving additional information. So, "The dog that I got from Mike is playing in the yard," makes it clear that you're talking about the dog from Mike, rather than any other dog. "The dog, which I got from Mike, is playing in the yard," says that there's a dog playing in they yard, and adds the additional bit of information that this dog happened to be given to you by Mike.

Really? Because I haven't found much.

Well, not a lot. But some. Mostly Dean/OMC, with the occasional hit of Sam/OMC from the Stanford days. Stele3's 1300 Days has a bunch of Dean slash. I disagree with her John characterization, but that's a great story sequence anyway.

I've also seen a bit of Dean-as-rentboy around the internets. And Hossgal's got a link to a Dean/Gordon thing on her recs list, which almost works.

If you get pasteurized milk that is grass instead of grain fed, the levels of CLA and beneficial fats are higher.

Oh. Well our cows ate mostly grass. With some corn and oats.

(plus the occasional model rocket that got lost in the hayfield and chopped up with the rest of the hay...)

Dr. Grammar on "That or Which" (I'm certain this will cause argument)

That or Which?
According to The Grammar Bible,
"That refers to people, animals, or things.
The woman that witnessed the shooting will testify tomorrow.
The camel that carried us through the desert has died.
The explorers found the cave that hid the treasure for so many years.
Which refers to animals and things, never to people.
The dog which tipped over my garbage can needs a shorter leash.
The crowd cheered as the plane which had flown around the world landed (Strumpf 198).
Common Errors in English argues that "there is little evidence that this distinction is or has ever been regularly made in past centuries by careful writers of English. However, a small but impassioned group of authorities has urged the distinction; so here is the information you will need to pacify them.
If you are defining something by distinguishing it from a larger class of which it is a member, use 'that': 'I chose the lettuce that had the fewest wilted leaves.' When the general class is not being limited or defined in some way, then 'which' is appropriate: 'He made an iceberg lettuce Caesar salad, which didn't taste right'" (Brian 61-62).

Further debate on That versus Which (supporting Megan and Hil)

I will note that it seems to be an issue of high level quibbling.

"According to the more quibbling self-styled grammar experts, that is restrictive, while which is not."

No, it truly doesn't. It's awesome. Have you had it?

Okay, maybe I've only had raw buffalo milk, which tastes gross.

If you can't put a comma in front of which, it should probably be that.

Just leave out the "probably." This has become one of my pet peeves ever since I was taught the difference.

"That" is used for identifying information. "Which" is for giving additional information. So, "The dog that I got from Mike is playing in the yard," makes it clear that you're talking about the dog from Mike, rather than any other dog. "The dog, which I got from Mike, is playing in the yard," says that there's a dog playing in they yard, and adds the additional bit of information that this dog happened to be given to you by Mike.

And notice the comma.

Dr. Grammar on "That or Which" (I'm certain this will cause argument)

Dr. Grammar should lose his license.

Which refers to animals and things, never to people.

Right. Because in the case where you'd use "which" to refer to an animal or thing, you'd use "who" to refer to a person. That's not a which/that distiction.

(I'm certain this will cause argument)

We had this exact argument on WX. It was long and unpleasant. Blood may have been spilled. Let us never speak of it again.

Heh. In support of Jessica's point, I cite:

Bugbears.

Arguments over grammar and style are often as fierce as those over Windows versus Mac, and as fruitless as Coke versus Pepsi or boxers versus briefs. Pedantic and vicious debates over knotty matters such as Prepositions at the End, That versus Which, and Split Infinitives may be entertaining to those who enjoy cockfights, but do little to improve writing. Know as much as you can about the rules, but strive above all for clarity and grace. Think always of the effect you'll have on your audience. Over time you'll come to trust your ear, which will be disciplined by reading the best authors and by constant practice at writing. See also Prescriptive versus Descriptive Grammars and Taste.

Just leave out the "probably."

That's a habit from teaching French, where there is almost (see, I can't help myself!) always an exception.

For Flea's Sake:

There are two rules of thumb you can keep in mind. First, if the phrase needs a comma, you probably mean which. Since "Penn's ID center" calls for a comma, we would not say "Penn's ID Center, that is called CUPID."

Another way to keep them straight is to imagine by the way following every which: "Penn's ID center, which (by the way) is called CUPID. . . ." The which adds a useful, but not grammatically necessary, piece of information. On the other hand, we wouldn't say "The word processor which (by the way) is used most often is WordPerfect," because the word processor on its own isn't enough information — which word processor?

A paradoxical mnemonic: use that to tell which, and which to tell that.

I don't think I get that last one but I don't care!