Two big questions here:

1) Where are the dremora? I ended up with 2 daedra hearts early in the game, and saved them until I could craft ebony gear. Then I bought a 3rd one from a store. I've yet to find a dremora anywhere in Skyrim. Are there certain places they populate or are they totally random? I'd like to make some more daedric gear! And would like to fight some dremora.


2) I'm at the point in the main quest where I fought Alduin, and he left. Do the dragons remain in the game after this quest or do they all disappear? I never did find enough dragon scale to build a complete set of armor and weapons. And at one point, every time I fast travelled or ventured outdoors, a dragon would attack me. Now, I can't find them. I did find one, went to a large open area hoping he'd land, tried attacking him from the ground, but he eventually flew away. I haven't seen a dragon in several hours of gameplay.

1) Under your bed mwhaha. Seriously though, do some daedric quests including Mehrunes. You'll get around 4-5 hearts.

2) Yes, dragons are very much still in the game after Aldun's defeat.

There are a few dremora near the end of Azura's quest too. Otherwise, there are very, very few instances where you'll see them.

Once you did the Mehrunes Dagon Daedric Quest,there will be regular respawns of Dremora at his shrine.
So every once in a while you can gather about 4-5 hearts there,along with several gold and ebony ingots and some enchanted gear.
This is the most reliable source of hearts,hoping to find them in alchemist shops is...a long shot.

The alchemist shops in Whiterun and Solitude sell Daedra hearts about every fourth or fifth visit. I recommend buying them when you see them and then save them until your smithing level reaches 90 and you have unlocked the Daedra smithing perk.

If you're looking for Daedra hearts and coin isn't an issue, check out Enthir (I think that's his name) at the Mages college. He usually has 2 in his inventory to buy.

Enthir in College of Winterhold also sells Deadra hearts; during night hours. they go around 800-something i believe. if you got a lot of excess coin just buy him out and wait for 2 days and buy him out again, rinse and repeat

I finished the main quest, and I cannot fast travel to a single place without a dragon immediately attacking. Then when I run to my next destination, another dragon! I've seen more dragons in the two days since I've completed the main quest than all the time before put together.