I just found this out, sometimes when u join fractions u get to hear npc's talking to eachothers..rarely u will see some interaction between themselvs that actually matter to you or that involved u in some sort of way..
i dont know if u all checked this out or not but adrianne the daughter of proventus avenicci from dragonsreach, she tells u to bring a steel greatsword to balgruuf the jarl of whiterun, but u need to deliver it personally to her father the jarl's steward.
once u give it to him he will say that he will give the sword to the jarl when his mood is acceptable.
so i just did some random quests and i returned to dragonsreach to enchant and disenchant some weapons and tools ( at that time the court wizard gave me a iron axe as a token of my friendship o-o) but when i was enchanting i suddenly heard..a big yelling coming from the main hall.
I quickly stopped what i was doing and i heard jarl balgruuf talking to proventus avenicci "they said something about a sword", and i was fast enough to listen proventus mentioning his daughter's name ( i immidiatly found out that this was about the sword she made for the jarl that i had to deliver )
However...it seems that the jarl was not content with it...
he yelled at avenicci saying that he never wanted to see that piece of trash again.
What a slap to the face of avenicci and adrianne..and more in specifically to me since i was the one bringing the sword to the first place.
Well maybe not..adrianne is the one that should feel bad..
but quite interesting..i've never heard this dialogue before..
u ever heard any hidden dialogue from npc's that are NOT towards u?

You hear dialogue all the time if you just take your time and hang around in places instead of just rushing around doing quests. I have missed this particular piece of dialogue, though.

true. Skyrim keeps us busy and for those who are patient we get rewarded instead not with gold from quests but rather with more interesting facts about the game.

If it's "hidden" then it should be in the spoilers subforum. However, I have no clue how to get that dialogue, Proventus always carries that bulky twohander on his back and never does anything with it. I think I should visit Dragonsreach more often ...

Balgruuf makes it obvious in that interaction and some others that he wants peace for Whiterun. This is especially obvious in the Civil War questline.

There is one in riften where mjoll calls maven a (censored with a B right to her face and maven walks off stunned and I just smiled

If you see Helga outside in the Riften market, stop and hang out for a second. There is some really hillarious dialogue she has with some other woman about some deliveries that have arrived.

Theres a lot of dialogue that reveals stuff surrounding the game and the world, for instance some dunmer say "I wish I never left Mournhold" meaning its possible the Mournhold is still around while Festus talks to another DB agent about doing a Redoran contract and having to go as far as Vvardenfell meaning that Redoran or remnants of Redoran are still around and ships to Vvardenfell still exist, thus hinting that its possible that the Dunmer are resettling in Vvardenfell.

Walk everywhere when you are in busy places. From most of the youtube videos I see, people seem to run everywhere. When you do, you only hear the first line of a conversation that quickly gets dull (Do you often get to the cloud district). If you walk, or just generally hang around, you hear all sorts of interesting things, especially as mentioned in Riften. Even after officially passing the 950 hour mark (according to Steam), I still hear people say new things.

It pays to be patient in this game.