Where, besides the arena is a good place to get some money. Like a good quest or something?(not main quest) =)

go roaming around and goinginto dungeons, you should find alot of stuff there

Good,quick money?
Join ''Order Of Virtuos Blood'' faction.It's a faction sworn to kill vampires.You must have bit fame to join:Then a Dunmer woman aproaches you in the Imperial City and asks you to go to Suridur's House.Follow the quest.When you finish it you can sell each Vampire Dust(There is a lot in the quest,or try the Imperial City sewers)by a price of 250 gold.4 Vamps(And there are more in the quest) = 1000 gold

If that doesn't work for you,then try stealing some food and mixing some potions.....I have Alchemy as a primary and i got a small fortune by just selling potions......

Hope this suits you

Urgh too many threads on this.
Find stuff. Sell it.

If you want cheats/glitch/bugs, there are two (I won't re-type them here). One is the sell bug in which you sell a weapon that's equipped while you're on a horse (it never gets removed from inventory) at Skingrad, and the other is to kill Dorian in Imperial City. If you want details, look at old threads.

I'm sorry, but you are all wrong. To get money really fast;
1) Buy a horse
2) Equip a very expensive sword(>500gold)
3) Mount horse
4) Travel to Kvatch where the people are standing around outside
5) Talk to the female orc while on your horse and sell your equipped sword
You get the money, but it never leaves your inventory=instant cash

If I lose all my deadric swords and armors, ebony claymore and various warhammers Im going to blame you.

lol, its called save first...

Pffffft,why just not enter cheat command?It would save you some time!

DON'T USE CHEATS PEOPLE!!!

But theyre so much better than actually trying to get the money legitimately.

PS, the glitch does not work with armor, because it can be equipped while on a horse, only with weapons does it work.