I am a devoted player to series of Elder Scrolls and love Skyrim and think that it is one of the best games out there today, but I have found that I have done a majority of the side quests and practically all of the main quest lines.
I have done the companions, the thieves' guild, the dark brotherhood and the college of winterhold quest lines. What other cool quests are out there that just are fun, they don't have to give cool items or anything like that, but I am looking for fun cool quests to keep me going util Dawnguard gets here.
(Free cookies for anyone that gives me fun stuff haha)

Have you tried any mods? There are quite a few cool things to try out with mods now that the game is about a half year old now.

Xbox user so...

Then buy it for the PC. Now, when are you going to give me some of those free cookies?

Your Funny, but my pc is well lets say just not good enough to run the game, so...
But believe me I'd buy it for pc if i could.

Have you done all the Daedric quests? All of them are pretty entertaining and especially amusing if you know them from the previous games.

give me a couple of specific places to go or what to do to get it started.
I did do the ghost dog quest and the "a night to remember" one.

you should go to markarth and there will be a guy looking for some help then you can start the houses of horrors quest

You should try just exploring the countryside...that's where I have a lot of my fun.

Azura: Ask Inn Keepers about rumors... or travel a little south of Winterhold and climb to the peak of a moutain and you will find a giant statue of Azura.
Molag Bol: In Markarth a vigilent of stendar should be standing outside a house, asking people if they have seen anyone enter or leave the house
Meridia: Between Solitude and Dragons Bridge. Its a statue, aproach it and it will speak to you, reward will be useful during Dawnguard, if your a vampire hunter
Clavicus Ville: In Falkreath follow up on Lod asking about a dog.
Sheogorath: An old beggar in Solitude should be complaining about his MASTER being on vacation to long, talk to him.
Hircine: Go to the jail in Falkreath and talk to the guy in the cell.
Sanquine: You already completed, but have a drinking game with the guy in Riften.

Those are only the ones i ever completed, there are more tho. Read the book of the deadra to study these deadra.

Use command console to create all out assault war on your monitor.

thanks guys for the great info.

You could go on a killing spree if you like; you'd have two options.

A. Get as much bounty as you can by massacring everyone in public

B. Kill everyone covertly with assassination or illusion magic.

Killing guards with illusion magic is fun A simple fury spell, and the guards of the city would descend upon the poor guard like a pack of hellborn death machines, screaming and hacking away. If you were feeling particularly evil you could soul trap the poor sod as well.