Try www.mgketer.org. It's the Rabbinic Bible online. It presents the Aleppo Codex with Targums and commentaries. From the home page, click on תנך in the middle, and then עיון.
You'll get the first chapter of Genesis. Up in the left-hand corner you should see a menu that looks like this:
Click on the item תיקון קוראים. It should give you a column next to the text itself that shows the text without any vowels or accents - as it is written in the Aleppo Codex.
Using the menu item ספר you should be able to get to any book of the Old Testament, and using the menu item פרק you should be able to get to any chapter.