sfby wrote:
Once I've got my bags of horse manure, how do I know when it has rotted
enough to be mixed with my compost? Last year I just left it in a spare
bin for 6 months, but it didn't look (or smell!) much different to when
I started.

How trully strange. 6 months you said?! Our manure 'turns' into crumbs
within 2/3 months and even though we still got lots of straw in it but
the pooh has crumbled entirely. It's in a wooden crate, with gaps
around it, covered with a bit of old carpet and under an hawthorn. The
bin you've put it in, is it plastic and completely sealed? Because
there perhaps lies your problem. It needs to breeze a bit, with rain,
air, sun.

Here a fantastic site which gives you all you need to know.

http://www.primalseeds.org/compost.htm#kic