We don't have many right now.
They will evolve.
Here are the basics until they make it onto the website.
Spaces, not tabs for indentation. Yes, this is religious. The earlier deciders didn't agree. Everyone wanted something different. We settled on spaces.
Indentation level by language right now-
Java : 4
Smalltalk : 2
Html : 2
CSS : 2
There are probably more, but those are good simple basics.
In general, follow the style you see. If you want to change a style, you can open a discussion on it, but please...
these things tend to take up a ton of time with little reward so make sure whatever your change is will provide a big bang for the buck.
I've seen communities come apart over stupid discussions about where to put braces.
-Sean-