I'm sure this is requested alot, but I couldnt find a thread for it at the time, so here goes.
I checked Skyrimnexus for anything of this sort and I couldn't find anything. I put alot of time and effort into making my character look the way It does and I usually don't wear helmets in RPG games because of this. There are advantages having the helmet on though, like the full set bonuses, plus the helm itself. I don't want to miss out, but I don't want the helm to be visible.

Can this be done easely as a mod?

If it is like Fallout and Oblivion, you would need to make the helmet float over their head with invisible textures since they usually have no hair or a different hairstyle used when helmeted. Then you would need to do the same thing for every helmet in the game. It is not something like Dragon Age or Mass Effect that can be achieved with a single button click. Once the Creation Tools are available and Nifskope is updated for Skyrim, I am sure you may seem something like this come out.

I, too, would love something like this.

This can be done very easily, but it requires the SDK kit. Nifskope may help too if the SDK kit is lacking the usual features though.

YES, I would love this! So so much! I'm running around without a helmet and my Heavy Armor perk doesn't like that. :E

Another approach would be a Skyrim version of Kafei's Armored Circlets mod from OB..... that mod gave the general goods vendor in Skingrad, a complete set of circlets/tiaras/headbands that matched the stats of all the normal helmets. So, when you found/looted/bought/whatever an Elven helmet (for example), you could pop over to the store and buy the circlet version. Same stats, but you could see your hair.

(I've seen some mage circlets in shops, so there are models that could be used.)