Ashhar Farhan VU2ESE has an interesting page setting out what basic equipment he considers a QRP homebrewer needs. See http://www.phonestack.com/farhan/lab.html. The only additional piece of equipment that I have found really useful is a small box to measure inductors and capacitors. The LC Meter kit produced by the Cambridge and District Radio Club has proved invaluable. A small spectrum analyser would also be useful, but these do not come cheap, although there are designs on the internet to make simple ones.