The London Health Observatory has released a Guide to Reviewing Published Evidence for Use in Health Impact Assessment. The guide has been through quite a rigorous testing and peer-review process and a revised edition, incorporating user-feedback, is planned for 2008. I haven't had a chance to use if yet and I'd be interested to hear about your experiences using it.
The European Public Health Alliance has an interesting page comparing the health impact assessments that have been done on US and European food and agricultural policies.
Mary Mahoney, from the Deakin University HIA Unit, recently spoke about a retrospective HIA that she has undertaken on drought relief in rural Victoria in Australia. The ABC has a page with details on the conference and Mary's HIA, along with an MP3 file of their interview with Mary (MP3, 1.6 Mb).