My background is in public health and GIS, so one of my favorite open access GIS journals is the International Journal of Health Geographics. The breadth of topics and analysis covered is impressive and it is a good place to start when conducting a literature search. In addition, the Public Library of Science Journals (PLoS) frequently contain spatial analysis.
One problem with health and GIS is performing literatures searches. Since geographers and public health professionals use many terms to describe GIS, it can be very difficult to search for and identify relevent articles. For example, a search of PubMed finds only 1,200 articles for 'health and GIS' but almost 8,000 for 'health and geography.' So, watch what terms you use to search!
Besides health, there are an extensive list of GIS journals, some pay-per-access and others open access. Although published only a few times per year, I came across the URISA journal which is an interesting read for anyone involved in GIS in government. The Journal of Geographic Information System has an international scope.
Lastly, as I have considered writing, I have found some 'open source' journals charge to have an article published while others absorb the cost. Fyi, and something to keep an eye on when you start to write.