Of course all former core content modules, now know as "Value_Addons", work with .8 and so do most older modules. But only few already use the new features like DBUtil or the categories manager. The Quotes module of the Value_Addons is an example for all major new techniques being used. Most of all the use of the categories can be studied there.
And there are also the first 3rd party developers who started to work with .8 code:
If you are also already programming for .8 I would love to read something about it in the comments here or in your own articles.