Now that the code freeze has lifted, I've just merged in a ton of
shiny goodness:
1)
You can now use "is_set" inside an only_if expression to check if a
given variable is available.
Example: is_set('ansible_eth0')
This eliminates the need for the ugly 'not
'$ansible_eth0'.startswith('$') hack to check if a variable was/wasn't
defined.
2)
If you have a command that removes a file, rather than adding it, and
you want it to be called idempotently, there is now a removes= that
works just like creates=, only in the opposite way.
3) postgresql modules now take an optional port= parameter
4) /proc/cmdline info is now available in Linux facts
5) public host key detection for OS X in the setup module
6) to_yaml and from_yaml are available as Jinja2 filters, in addition
to to_json and from_json which were already there. I don't think many
people will need these, but if you have a variable stored as a YAML
list and you need to write it to a JSON config file, this is for you.
7) as I mentioned a bit earlier -- server side action code (template,
etc) are now fully pluggable -- tests are happy, but let me know if
you see any problems.
Lots of new stuff, and 0.8 is only a few minutes old 
--Michael