Where can I find and hopefully listen to all the comments made by each separate voice? I really don't want to record my own and for what I need the stock comments would probably work just fine. I just need to listen to them to pick the one's that are useful to me and add them to my NPCs. They can be added to other characters I hope?

One way would be to extract the files from the Voices.bsa file and convert the files into something you can play in a media player. There's a tool for batch conversion on Skyrim Nexus. I think it's called Unfuzer, but I've used another tool in the past. The downside of this method is that you won't know what the line of dialogue is until you've listened to the file, so you can't search based on the line.

MrJack nailed it. Use BSAOpt or a similar tool to extract the contents of voices.bsa, then use Unfuzzer to mass-convert them. Beware, the FUZ files are compressed but the output files are uncompressed WAVst. You'll need about 600MB for each generic NPC voicetype, plus a varying amount for all others. Don't try to extract them all at once unless you have over 20GB of free space.

What if you hear a NPC say something ingame and you want your NPC to make the same comment?

Sometimes a comment may be a shared info -- then you can copy it directly through a drop down list.

In many cases, you will have to extract the voice files from the .bsa and rename them to work with your new dialogue.

You can preview what lines sound like by opening the line and clicking on the section that lists voice types and whether or not the line is recorded for it.

Someone should produce a modder's resource spreadsheet with this info. That would be a huge effort, but, wow, what a help it would be!

Well it's easy to dump all the script text and the associated filenames from the CK to a tab-separated text file, and from there import it to a spreadsheet, but it's 59,607 rows and Google Docs essentially says "Heh, yeah, we're not gonna do that." I'd have to build a database and whip up some php to make it filterable. Maybe if I have dead time at work or something...

This might be seriously awesome.
I am wanting to create an new housecarl, but I want to know all of the sounds I need to records, from greetings, to combat grunts, etc.
It would also facilitate new voices for merchants, trainers, etc.
It would facilitate more racial voices (khajiit, argonian) that are under-represented.
I can foresee that voice actors could offer a set of their recordings for incorporation if they knew what voice "scripts" they needed to cover
Really creative follower mods would be possible using interaction with vanilla NPCs (like VIlja does with Lydia, Aela, and Farkas) if you knew what scripts those characters have.

I had http://fallout3.nexusmods.com/mods/images/14137-1-1281864383.jpg for fallout 3 that would let me sift through vanilla dialogue. It doesn't have script info or anything like that. Currently, it just lists stock dialogue and allows filtering to find a specific topic, but I'm hoping that eventually, I would be able to -remap stock dialogue to new modded dialogue.

Idea being:
* Export all vanilla dialogue from the CK and import it into the sifter
* Export new mod dialogue place holders from the CK and import that into the sifter
* In the sifter, map vanilla dialogue to mod dialogue
* Export mapped mod dialogue from the sifter
* Import mapped mod dialogue into the CK

So I have to make the new dialogue in the CK, but for the response text, I just use a place holder like "Politely Disagree with Player". In the sifter, find a line that will fit and then map that to the mod dialogue:
Mod: Politely Disagree with Player | Neutral 50 | Data/Sound/Voice/SomeMod.esm/FemaleNord/dialoguege_topic_000c8z3x_1.wav
Vanilla: No offense, but I think you're wrong. | Disgust 10 | Data/Sound/Voice/Skyrim.esm/FemaleNord/dialoguege_dialoguegeneric_000a9b2a_1.wav

So that when the exported sifter dialogue is imported into the CK, the final response would be:
Mod: No offense, but I think you're wrong. | Disgust 10| Data/Sound/Voice/SomeMod.esm/FemaleNord/dialoguege_topic_000c8z3x_1.wav

I think it would also be possible to generate a batch file that copies the vanilla dialogue files to the mods location (and maybe archive them into a bsa?).

It still has a ways before it works with skyrim and can re-map topics though. :/