So I already googled it, wikied it, etc, but still not help.
I heard Elfir, or whatever his name is in the College of Winterhold sells them, but I can't find the guy.
None of the Alchemists have them (I've only gotten to Wihiterun (where I'm based), Falkreath and just got to Winterhold's College.
I've already smithed up to Daedric, so it should be unlocked.

Do you guys now where to find that Elfir guy? He just wanders around?
Anywhere else near any of those places I mentioned above?

Thanks, guys!

Depending on your level the alchemists will have the semi-regularly. Enthir wanders around town a lot, you may want to check the Inn. I first found them for sale in Solitude.

Enthir can usually be found wandering about the Hall of Attainment in the college, or at the inn at Winterhold.

In the Hall, he will always be in his room on the second floor. If he's not there, wait a couple of hours and he will eventually show up.

You can farm them at a place - I or someone else will reply with the name/location if you don't mind a spoiler - but I bet the Khajit that camps outside Whiterun may sell them. I've seen him with 'advanced' items early in the game (ie ebony ingots when no one else was selling them).

NP, give me location. If you can give me location without spoilers that would be awesome but not necessary.

I know if you do the quest Pieces of the Past, Mehrunes Dagon will have two dremora try to kill you at his shrine and they will respawn. Also the alchemists in any of the orc strongholds sell them.

Shrine of Mehrunes Dagon as mentioned above. Be advised, that while they are supposed to respawn every 7 game days I've been told in another thread that if you go back sooner than 7 days they will bug and no longer spawn there...if you intend to farm them regularly.

I'm sure you can find a map online, but it's on a mountain ridge approx 095 degrees relative of Morthal and 200 degrees relative of Dawnstar.

Cool. How do I get Pieces of the Past?

Dawnstar has a museum, go there. Not sure if you need to wait for an invitation there. A courir will bring it for you.
On another note, I haven't had such a shortage, I've had about 10-12 daedra hearts without doing anything special to get them.

Yeah, I got the museum note thing from the courier already. Haven't gone to Dawnstar yet. So that museum guy has the Pieces of the Past quest? That's cool. Wonder where the heck those Orc forts are if their alchemists sell daedric hearts. Hmmm.

Look for little dome-looking things on your map. They look like rounded pup-tents with a narrow arch over them and a small triangular opening at the bottom center...NOT the inverted trident-looking things.

There are four orc strongholds in Skyrim. I don't remember their names though. One is South South-East of Markarth, another is far to the North and West of Solitude, then there is one South-East of Windhelm near the Boethiah shrine, the last is in western parts of the Rift.

This, although you seem to need to be about level 25, and it only seems to apply to the alchemists in the walled cities.

Babette of the Dark Brotherhood sometimes sells them too.