Now that we've moved to mercurial for all yt development (which I'm pretty pleased about) I have placed a wiki page here:
with all the current active branches. But basically, it comes down to:
"stable" => the previous yt head, which has the old names "yt" => the new head, reorganized and probably with some lingering import issues "kd-render" => Sam's branch for kD-tree volume rendering
If you are able, I'd prefer if you could use and fix any issues that arise with imports directly in the "yt" branch, but if you'd rather continue using "stable" that's of course fine as well.
PS Sorry about the confusion on the graph on the main web page. I think I could have mangled history enough so that branches would be closed AND have their last heads in the distant past, but it's too late now. Maybe some day we'll have the option of hiding topological heads on closed branches in the graph view, but that day isn't today.