If you own a Bible, and it has an index, these references are not hard to find; but if you insist--
Killing a slave is murder--Exodus 21:12. (since this passage falls in the middle of a section concerning slaves, it was assumed to apply to slaves as well; but in any case, it is explicit in 23:20.)
Injured slave goes free--Exodus 21:26.
Law on captured women, Deuteronomy 21:10-14
Sabbath rest for slaves--Deuteronomy 5:14.
Prohibition of returning an escaped slave to his master--Deuteronomy 23:16-17.
The other laws I mentioned are not explicitly given, as I thought, but are Talmudic and derived from the above. I regret that error, but I'll stand by my point.
Thank you!
While I have access to, I do not actually own a bible. I link what I'm using below.
Since your claim is concerning the bible, I'll respond to the claims you made that you say the bible supports. If you can find biblical references to the other claims, I'll consider them when you furnish the references. Again, I don't have an actual bible any more. If your claims are supported by the bible, please tell me where so we can discuss them. Your making the claims, not me!
First,
Killing a slave is murder--Exodus 21:12. (since this passage falls in the middle of a section concerning slaves, it was assumed to apply to slaves as well; but in any case, it is explicit in 23:20.)
I disagree that 21:12 applies to slaves. It clearly states "He that smiteth a man, so that he die, shall be surely put to death." Says nothing about a servant. You are correct, I believe, in stating that 21:20 (assume that's what you meant, since 23:20 is in no way related to the topic of discussion) deals with slaves! Let's look at it!
21:20 And if a man smite his servant, or his maid, with a rod, and he die under his hand; he shall be surely punished. Doesn't say how, and doesn't say it's murder, but there is an "eye for an eye... reference later that could be said to apply. But what you neglected to mention is 21:21! Strange how that works. Let's look at 21:21 shall we?
21:21 Notwithstanding, if he continue a day or two, he shall not be punished: for he is his money.
What's that? If the slave lives a day or two after the beating, and then dies, it's all cool, because after all it is just the mans money. Kinda goes against the general theme of your claims doesn't it?
But, let's continue anyway, shall we?
Injured slave goes free--Exodus 21:26
26 And if a man smite the eye of his servant, or the eye of his maid, that it perish; he shall let him go free for his eye's sake.
27 And if he smite out his manservant's tooth, or his maidservant's tooth; he shall let him go free for his tooth's sake.
I added 21:27 because it goes so well with 21:26

What they actually say is that if a man causes his servant (man or maid) to go blind in one eye, or loose a tooth, they are to be let go. Not quite as general as implied. The slave has to be injured by it's owner, and apparently only the loss of an eye or a tooth is covered. But, in a broad sense, you are correct.
Law on captured women, Deuteronomy 21:10-14
Well, you really have to go back to 21:7 to get the full meaning here. Let's look
21:
7 And if a man sell his daughter to be a maidservant, she shall not go out as the menservants do.
8 If she please not her master, who hath betrothed her to himself, then shall he let her be redeemed: to sell her unto a strange nation he shall have no power, seeing he hath dealt deceitfully with her.
9 And if he have betrothed her unto his son, he shall deal with her after the manner of daughters.
10 If he take him another wife; her food, her raiment, and her duty of marriage, shall he not diminish.
11 And if he do not these three unto her, then shall she go out free without money.
12 He that smiteth a man, so that he die, shall be surely put to death.
13 And if a man lie not in wait, but God deliver him into his hand; then I will appoint thee a place whither he shall flee.
14 But if a man come presumptuously upon his neighbour, to slay him with guile; thou shalt take him from mine altar, that he may die.
Really, 7-11 are the ones that pertain. 12-14 are different subjects completely.
First off 7 says it's about a man selling his daughter to be a maidservant. Obviously this indicates that not only can slaves be captured in battles/wars, but it's OK to sell your very own daughters as slaves. Yea, that shows the bible in a positive light in regard to slavery!
OK, verse 8, I have no damn idea what it means.
Verse 9 is a winner! If the buyer of the other person's daughter gives her to his son to marry (basically) the buyer has to treat her as his own daughter (which I assume means she could be subject to being sold again, but that's presumptuous of me isn't it

)
Verse 10 says that if the son takes an additional wife, the food and what have you, that the slave was getting before the second marriage can not be decreased. Much as you stated.
And verse 11 puts in the "what if" to verse 9. If those things don't happen, she gets to go free.
Sabbath rest for slaves--Deuteronomy 5:14.
14 But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, nor thy manservant, nor thy maidservant, nor thine ox, nor thine ass, nor any of thy cattle, nor thy stranger that is within thy gates; that thy manservant and thy maidservant may rest as well as thou.
Got to agree with you on this one!
Prohibition of returning an escaped slave to his master--Deuteronomy 23:16-17.
I think you meant 15 and 16 (or our Kings Jame's are different, and I'm using
this one)
15 Thou shalt not deliver unto his master the servant which is escaped from his master unto thee:
16 He shall dwell with thee, even among you, in that place which he shall choose in one of thy gates, where it liketh him best: thou shalt not oppress him.
I read this to apply to slaves from other tribes or areas, entering into a Jewish, or Israelite camp/area. I'd have to read more than I want right now, to firm up an opinion on this, so I'm gonna give you a conditional agreement here
OK, where do we stand?
You claim - in the OP
It would be more useful, I think, to consider what the Bible does have to say about slavery; and there we find that, while the institution itself is accepted, its immorality is heavily implied in the strict limitations and prohibitions imposed on slaveowners.
These restrictions were unique in the ancient world; in other cultures, slaves were mere property, and their use and abuse was no more restricted that those of a table or chair. The death of a slave, even if the result of a drunken whim, was of no account at all. If one killed the slave of another, one paid the slaveowner for the loss of his property and nothing more.
I've shown that the bible clearly states that slaves are merely a commodity (Duet. 21:21 Notwithstanding, if he continue a day or two, he shall not be punished: for he is his money.)
I won't accuse you of using standard fundy methods to support an agenda. I'll take you at your word, and assume you truly believe what you said. Unfortunately you made the same mistake fundies accuse us atheist of. You picked and chose your supporting verses, and ignored the others. When taken in context, I believe that for the most part, the bible does little more than put a minimum of restrictions on what can be done to a slave. Does the bible require that slaves be treated better than other cultures of the time? With exceptions (one noted by another poster above) yes. Is it really a big enough difference to support your claims? I think not.