I've written a tool to help get data from mqtt to pachube. Existing pachube libraries offer good support for updating feeds that have a single datastream or updating all feeds in a datastream, but seem to offer limited support for updating an arbitrary datastream on its own. This can make life difficult when your data is coming in from sensors as individual messages.
mqtt2pachube allows you to choose what mqtt subscriptions to make and then match incoming messages by their topics to a pachube feed and datastream id.
At the moment it is still experimental, but seems to work. It has highlighted a shortcoming in the mosquitto client library, so requires version 0.15.90 (ie. the in-progress work for the next release). There is no Windows support for the moment and no binary packages either. If you are interested in giving it a try, you will have to compile it yourself. If you need help, please get in touch.
There are two examples of feeds created through mqtt2pachube using data from test.mosquitto.org